ASK THE RABBI

Little is written about whether lighting halachically unneeded candles on Chanuka is bal tosif. We will start with general rules regarding mitzvot.

Rishonim ask why it is permitted to blow beyond the first set of tekiot on Rosh Hashana. Tosafot (Rosh Hashana 16b) answers that just repeating a mitzva is not bal tosif. The Rashba answers that it is permitted because it follows Rabbinic instruction. (There is a machloket whether the Rashba also accepts Tosafot’s answer – see Minchat Chinuch #454 and Pri Megadim, Orach Chyaim, Intro. I:40.) There are also opinions (see Ra’avad, arguing on Rambam, Lulav 7:7) that using more of a correct mitzva object than required (e.g., two etrogim), is permitted. It is more lenient when the two objects are used in separate places (see Sukka 31b). On the other hand, maybe the fact that they are both on legitimate parts of one’s house connects them (see later). According to Tosafot and the Ra’avad, then, there is no problem lighting extra chanukiyot, and the Pri Megadim (ibid.) suggests that bal tosif never applies to Rabbinic mitzvot.

There are more basic grounds to say that extra chanukiyot is fine. Even those who argue with Tosafot do not forbid bal tosif for doing more than required regarding every mitzva. Is it forbidden to say Kri’at Shema or mention the Exodus more than required?! Sometimes, more is a good thing. Classical sources and minhagim support the thesis that we look positively on more pirsumei nisa than required by strict Halacha. The Terumat Hadeshen (I:101) says that a man away from home who can fulfill the mitzva with his wife’s lighting can prefer to light himself based on the concept of mehadrin. Also, when one has lit in the correct place but there is a side of the house where the candles cannot be seen, he should light there too (Shulchan Aruch, OC 671:8). We do this without a beracha, apparently because it is not a real mitzva (Rama ad loc. based on the Ran, Shabbat 10a of Rif’s pages). There is a minhag to light candles in shul for Shacharit, without any halachic mandate. These are indications (not proofs) that strengthen the logic that bal tosif should simply not apply to Chanuka lightings, which would explain the near silence on the topic. Therefore, Rav Carmel (one of our roshei kollel) ruled that you need not be machmir and can light freely without a beracha to enhance your experience.

For one who is concerned, despite the above, that there could be a problem, we tersely present some practical ideas. Many posit that if one repeats a mitzva “with a twist” to remove a doubt, there is no bal tosif. (The Shulchan Aruch’s (OC 34:2) idea of putting on Rashi and Rabbeinu Tam tefillin at the same time is different because they are mutually exclusive, whereas inside and outside lighting can both be fulfillments.) See (Bemareh Habazak IX:35.) a machloket about putting mezuzot on both doorposts when one is unsure of the correct side. If you have some doubt if your lighting outside is definitely done in the right place/way (see our discussion of the pros and cons on the inside-outside question in Living the Halachic Process, III, D-11) this might eliminate bal tosif questions (see Divrei Yatziv, OC 287). This works better if your wife hears your beracha outside and then lights inside, with the two of you having in mind to be yotzei with the better lighting.

If the lighting is as an extra, other “machmir” ideas include lighting without kavana for a mitzva before the mitzva’s time or after the real candles go out. We discourage putting the extra chanukiya in the window, as it goes against the local practice of one, outside lighting, and to use the type of artistic chanukiya (see LTHP, I, D-10) that people like you would use for atmosphere, not mitzva.

There is a consensus that Kaddish Titkabel (after U’va L’tziyon), including the line that Hashem accept our prayers, relates to chazarat hashatz. For example, the Shulchan Aruch (Orach Chayim 123:5) says that a chazan does not take three steps back after chazarat hashatz, as one does after the silent amida, because he will do so at Kaddish Titkabel (Mishna Berura 123:18). (For this reason, the chazan should not talk between the end of chazarat hashatz and Kaddish Titkabel (ibid.).) The Rama (OC 55:3) says, regarding the rule that when the minyan quorum is lost in the middle of a unit we finish up the unit, that this rule allows saying KaddishTitkabel if chazarat hashatz began with a minyan. Therefore, your shul’s dissenters have logic to posit that one who did chazarat hashatz should finish the Kaddish that completes it. On the other hand, it is possible to split units among people. If needed, the chazan can be switched even in the middle of chazarat hashatz without returning to the beginning (Shulchan Aruch, OC 126:2).    

The question is whether a shul should ever choose to do this. An early source providing a scenario when this is called for is the Rama in the laws of aveilut (Yoreh Deah 364:4). In promoting the idea that an avel being chazan provides better virtue for the deceased than his reciting Kaddish, the Rama says that if an avel is not a fluent davener, he should be chazan for “Lamenatzei’ach and U’va L’tziyon.” Poskim assume that he means that the new chazan will recite Kaddish Titkabel. The Bi’ur Halacha (siman 132 in Kuntras Ma’amar Kaddishin, which deals with questions of preference in being chazan/saying Kaddish) says that with two mourners with the same level of precedence, one davens until Ashrei, at which point a second mourner takes over. Thus, the central decisors of Ashkenazi tradition uphold the practice of switching chazanim when there are multiple mourners. While I have heard Ashkenazi poskim (including in the name of the Aderet) not being pleased with this practice, it is a long-held, broad Ashkenazi minhag as found in sources and as I have seen in many places. (As the percentage of mourners at minyanim decreases, mourners often find a minyan to be the exclusive chazan, and this accepted minhag is used more sparingly.)

The issue in your shul arose because of the knowledge and experience of the Sephardi members. The broad Sephardi minhag is to not switch chazanim and have the second one recite Kaddish Titkabel (see Yalkut Yosef, OC 123:9; Yaskil Avdi VIII:20). Yaskil Avdi posits that the Ashkenazi minhag is simply wrong and should be stopped. He is most concerned with the line of “Titkabel …,” which relates to the chazan’s chazarat hashatz. Yalkut Yosef, while confirming the Sephardi minhag, says the Ashkenazi minhag is justifiable. First of all, the chazarat hashatz applies to the new chazan, as part of the tzibbur (and especially if he was attentive). The Asheknazi version of Titkabel is also more general than the Sephardi one. There are also opinions and indications that Titkabel applies to the silent Shemoneh Esrei, as it does at Ma’ariv, which has no chazarat hashatz.

Interestingly, Sephardim are consistent in their minhag in the following way. To them, an avel’s main obligation is to recite Kaddish, whereas many do not serve as chazan. Therefore, the need to “share the amud” is smaller. Note that the now almost universal minhag that all mourners recite Kaddish together started with Sephardim, who, again, stress Kaddish.

There are a few issues of muktzeh involved here. One is whether to consider a heating pad a kli shemelachto l’issur or a kli shemelachto l’heter. On the one hand, in order to use it, one must put it on, which it is forbidden on Shabbat. On the other hand, if one prepared it before Shabbat (by keeping it on or setting a Shabbat clock), then further use does not include melacha. (We are not delving into issues of medical activity on Shabbat. While not a trivial question, with the level of need involved, there are ample grounds to permit it – see The Halachos of Refuah on Shabbos, p. 26.). Rav Moshe Feinstein (Igrot Moshe, Orach Chayim III:49, regarding an electric fan) treats such items as kli shemelachto l’issur. However, regarding a case very similar to ours, an electric blanket, he raises the serious possibility that it is a kli shemelachto l’heter. This is also the opinion of Rav S.Z. Auerbach (Minchat Shlomo I:9) and Rav Asher Weiss (Shut Minchat Asher I:33), although none of them was willing to rely on this heter alone. In any case, it is permitted to use a kli shemelachto l’issur for a permitted use (l’tzorech gufo) (Shulchan Aruch, OC 308:3) and this would be a classic example.

A further problem is the fact that the heating pad has a filament that becomes glowing hot. In certain areas of halacha, this is considered like fire (see Shemirat Shabbat K’hilchata 43:4 regarding using an incandescent light for hadlakat neirot Shabbat in a case of need). We find that a lit ner (oil cup) is full muktzeh, which cannot even be moved for a permitted use (Shabbat 47a). This is because the flame is muktzeh (more than a kli shemelachto l’issur), and the oil and cup are a bassis l’davar ha’asur (something which is supporting that which is muktzeh). So ostensibly, the whole pad is a bassis for the heat-emitting electrical wires, which are the heart of the device (Orchot Shabbat 19:(246)).

We must understand why the gemara posits that a flame is muktzeh. One answer in the Chazon Ish (OC 41:16) is that the fact that one does not move a flame on Shabbat (since it can go out) makes it muktzeh. Another answer he suggests is that the flame is considered nolad, something that did not exist before, as the flame is constantly renewing. Rav Asher Weiss (in a letter to Zomet) says that it is because a flame is a separate unit that does not fit into one of the categories that would make it not muktzeh (i.e., food, a utensil).

Even according to the Chazon Ish’s explanations, the heat-producing electricity might not be like a flame (see Minchat Shlomo I:14, who analyzes this Chazon Ish). In any case, several contemporary poskim posit (including Igrot Moshe, OC III:50), mainly in the context of an electric blanket, that we do not view the heated wires and the electricity therein as a separate unit like a flame is. Rather, it is subsumed under the overall utensil of the blanket, which is either a kli shemelachto l’heter or kli shemelachto l’issur (see above), but, either way, it can be moved as part of its use. Rav Ovadia Yosef (Yechaveh Da’at V:28; see also Chelkat Yaakov, OC 118) adds also that the electricity in the wires are not comparable to a flame because the results are not visible. However, many, including Rav S.Z. Auerbach (Minchat Shlomo I:14), permit to move even lamps whose electricity gives off a noticeable light. In the final analysis, then, it is permitted to use the heating pad.

Rav Moshe Feinstein (Igrot Moshe ibid.) required attaching a reminder to the controls and the wall socket so that one not change the setting or unplug it. Rav Ovadia (Yechaveh Da’at ibid.) considers that a new gezeira and therefore unnecessary, although he also wrote that it does not hurt to be stringent. All agree that one does not have to be concerned lest he inadvertently pull it out of the wall, against his intention.

Although they are sometimes discussed interchangeably, there are two distinct, albeit closely related, mitzvot in which non-principals at a wedding should try to take part.  

The gemara (Ketubot 17a) discusses the mitzva of hachnasat kalla – joyously escorting the kalla from her father’s house to the place of the “chupa.” A large part of the townspeople were expected to join in, and this is important enough to warrant suspending Torah study and gaining right of way over a funeral procession (ibid.). It is a sign of kavod (see Tosafot ad loc.) for the participants in the important institution of marriage (there is a machloket whether marriage is a formal mitzva). While we no longer escort the kalla through the streets, poskim identify parallel events in today’s wedding ceremony in which one can fulfills this (see Taz, Even Haezer 65:2).

Presumably, one who is a full participant in a wedding ceremony fulfills this element of showing respect. There is not much precedent for a formal mitzva to watch the performance of mitzvot (while appreciation of mitzvot is generally a nice thing). However, if the chupa is not well attended or people are not attentive or are talkative (I have seen both), it is a zilzul to the institution of marriage, the chatan/kalla, and the families, who rightfully expect interest in the momentous moments.

Chazal held the celebratory seuda after the chupa in very hard regard. Regarding the provisions, significant time should be used to prepare for it (Ketubot 2a) and a burial of a parent can be pushed off so that the provisions are not wasted (ibid. 4a). The music is seen as deserving of far-reaching leniencies (see Rama, Orach Chayim 338:2; Igrot Moshe, OC II:95). Regarding participants’ mandate to be mesame’ach (bring joy), we find great rabbis praised for compromising their honor (Ketubot 17a) and relaxing the standard level of tzniut in dancing before the kalla and praising her (ibid.), including the controversial Chassidic minhag (with earlier sources – see Beit Shmuel 21:11) of the mitzva tantz. The gemara (Berachot 6b) warns of Hashem’s disapproval of one who “benefits from the feast of a chatan and is not mesame’ach him” and praises those who are mesame’ach. The Perisha (Even Haezer 65:2) limits this obligation to one who benefits from the meal. The Beit Shmuel (65:1) says that one should go to the wedding in order to be mesame’ach. The Tiv Kiddushin (EH 65:1) suggests that all can agree on a middle position – there is a mitzva to go, but only one who benefits and is not mesame’ach is criticized.

How each individual is mesame’ach is subjective (Ezer Mikodesh to EH 65:1), but it can include appropriate words, presents, dancing, or the very presence of an important person (ibid.). If one has a relationship only with the couple’s parents, one can presumably be mesame’ach the couple vicariously.

Let us return to the question of preferences. Regarding a brit mila, the famous idea of not inviting actually refers to the seuda, not the brit itself (Tosafot, Pesachim 114a; Rama, Yoreh Deah 265:12). The Rama cites this idea of angering Hashem by failing to take part only regarding a brit, as we generally assume, but Tosafot also applies it to the seuda of a wedding of a talmid chacham. This points to the prominence of participation in the seuda. On the other hand, the Tiv Kiddushim (ibid. 3) says that the idea of suspending Torah study is for the escort, not the meal. Perhaps, though, that is because escorting when the procession passes one’s place was likely not very time-consuming.

[We responded to the querier regarding his situation but are broadening (in brevity) the discussion. Last time we saw reasons for and against accepting the discharge of debt even though the original halacha disallows it. This time, we will explore practical issues including distinctions between cases. We cannot cover all elements and cases.]

Poskim are quite lenient regarding debts owed by corporations. The Pitchei Choshen (Halva’ah 2:(63)) says that all agree that in doing business with a corporation, which are defined by corporate laws, people expect that the law of the land will govern, even if the owners and officers are religious Jews. This obviously applies to investors in a corporation, but it also should apply to suppliers and even workers. When an individual owes money to a financial institution (e.g., banks, credit card companies), the laws of bankruptcy apply. After all, they plan based on the expectation that a percentage of their debtors will go bankrupt, and they factor this is when setting interest rates. Bankruptcy is valid in regard to corporate as well as non-Jewish creditors, since the governing law in their regard is the law of the land.

The matter is more complicated when an individual Jew lends money to another Jew, especially based on the latter’s need (see more on this distinction in Chelkat Yaakov, Choshen Mishpat 32) supplies goods to him on credit, or employs him. (When a creditor has a connection to the debtor or is a charitable person and can afford it, he could decide to forgive the money and count it as tzedaka, but that is his decision. We should also remember that the idea of forgiving debt is not foreign to Judaism, as according to Torah law, every seven years, debt is forgiven. When this is practically applicable is beyond our present scope.) If the one who is owed money did not make actuarial calculations and reasonably believed the debtor felt obligated to pay his debt, the matter of acting based on local practice is not so applicable. It is also unclear if the law, whose rationale is most societally compelling for growing the economy, is justified to contradict Torah law regarding personal consumer debt. Also, often a debtor knows he will be able to pay, just with difficulty. It is possible that the hardship of paying is not much greater than the hardship of loss to the creditor, and there are not moral grounds to not fulfill one’s obligation. If an individual debtor fully regains his ability to pay, it is morally correct to pay his fellow individual even if bankruptcy law does not require it.

Bankruptcy applies in regard to all of one’s creditors. During the process, one is forbidden to pay creditors selectively; the court dictates payment. Therefore, if one has a moral right to file for bankruptcy due to corporate debt, the loss to the individual creditor is a necessary casualty, at least initially. However, nothing legally prevents the debtor, after the receiver takes assets as instructed by the court, from paying those to whom he feels a higher moral obligation, which he should do as possible. (It can be difficult to deal with a case in which there are multiple such creditors and insufficient funds for them all.)

[We responded to the querier regarding his situation but are broadening (in brevity) the discussion. We will compare elements of bankruptcy law (focusing on the American system, which is more sweeping than many European systems including Israel) to Halacha, survey how Halacha reacts to that (this week), and relate practically to some common applications (next week).]

Of the two elements of modern bankruptcy law, one is found in Halacha. If a debtor lacks the funds to pay, he must liquidate or give many of his assets to his creditors, or beit din will, in many cases (depending on the type of debt and assets) oversee the seizing of assets. However, the debtor retains basic assets needed for daily living (mesadrin l’ba’al chov – Bava Metzia 113b). All bankruptcy systems do this and regulate the apportioning of payment among various creditors, in a way that differs from the halachic system.

The second element of American Bankruptcy is “fresh start,” which makes it unnecessary to make payments (“discharge”) beyond those prescribed by the bankruptcy court.  Talmudic Halacha does not recognized fresh start. If someone originally lacks funds but acquires them later, he must pay past debts using new assets.

There are a few possible ways for fresh start bankruptcy to become halachically viable. One is that in some cases, the creditors make a settlement with the debtor over the terms of reduced payment. Agreement actually does not make the question moot, because it can be considered agreement under duress. This is because the creditors have to deal with the “threat” of a possibly more detrimental, non-halachic bankruptcy judgment or that the debtor’s remaining assets will disappear before they receive payment (the bankruptcy system takes steps to prevent such disappearances). Regarding agreement under duress, a sale is valid, but a present given under duress (i.e., without a significant return) is invalid (Bava Batra 47b). After citing various opinions and distinctions, the Pitchei Choshen’s (Halva’ah 2:(62)) approach is that the parties’ agreement is insufficient to make debt reduction binding unless finalized without an act of kinyan (which may or may not exist in various cases).

A factor that might validate even debt discharge is dina d’malchuta (the law of the land). There are three main approaches regarding the concept’s extent. One limits it to the direct welfare of the governmental entity (opinion cited by the Rama, Choshen Mishpat 369:8). The Rama (ibid.) rules that it applies much more broadly – to cases in which a law is made to improve society (as opposed to for the government’s perception of justice). The Shach (CM 73:39) argues that even when done to ostensibly improve society, a law that contradicts the Torah is not acceptable (between Jews). The Chatam Sofer (V:44) follows the Rama’s approach, with a slight clarification. We follow dina d’malchuta when it addresses a societal need in a manner that the Rabbis would have instituted the matter if they had the ability. Most poskim (see Igrot Moshe, CM II:62; Rav Daichovsky in Techumin XVIII) follow the Rama’s approach, and in our beit din, we do so with the Chatam Sofer’s addition. However, it is not always clear when a law contributes to society and/or would the rabbis agree to it. (Regarding bankruptcy, the Chelkat Yaakov, CM 32 views it negatively, and the Igrot Moshe ibid. positively.)

A mishna (Berachot 34a) states that a kohen serving as chazan should not duchen even if he is the only available kohen unless he is confident that he will be able to return to his place in chazarat hashatz without undue confusion. The Tur (Orach Chayim 128) cites the Maharam MiRuttenburg as saying that the ability to not get confused does not erase the problem totally but only allows duchening when the chazan is the only available kohen. The Shulchan Aruch (OC 128:20) and the Rama (ad loc.) follow this ruling. The logic is that the slight endangering of the quality of the public tefilla is warranted only if it is needed to ensure Birkat Kohanim will take place at all.  

Some later poskim present ways of coming to a different policy. The Pri Chadash (ad loc.) reads the mishna differently. In practice, whether or not there are other kohanim makes no difference. The mishna starts by saying that even if there is no other kohen, a chazan who might have a concentration problem may not duchen. Once it introduces that this problem depends on the person, there is no reason for any capable kohen to forgo his mitzva of Birkat Kohanim.

The Magen Avraham (ad loc. 31) tries to explain a minhag he was aware of for a chazan to duchen even if there are others based on a societal change since the time of the gemara that many note. Nowadays, the chazan uses a siddur, in which case we can assume that he will be able to continue chazarat hashatz properly. While according to the Tur and Shulchan Aruch, this broad confidence in today’s chazanim is only enough to justify duchening when he is the only kohen, one can argue that it removes any effect of the problem and allows duchening in all cases. The Magen Avraham disagrees with this approach, because the poskim during hundreds of years of siddurim use did not write that the halacha had changed. However, he reasons that it is legitimate to follow it if this is the local minhag. The Mishna Berura (128:76 and Sha’ar Hatziyun 64) takes a similar approach to that of the Magen Avraham. This is also the practice of most Sephardi communities (see Ohr L’tzion II, 8:5; Yalkut Yosef, OC 128:62). However, the majority of Ashkenazim in Israel (especially, in Yerushalayim) follow the Pri Chadash and allow the chazan to duchen even if there are others who are doing so (see Dirshu 128:(84)). (Az Nidberu XIII:34 advocates a compromise. A kohen who is serving as chazan when there is only one other kohen should also do Birkat Kohanim, because many hold that Birkat Kohanim is a mitzva from the Torah only when there are two kohanim. However, he was unable to find a previous posek to explicitly make such a distinction.)

There are times when one whose minhag is to not duchen should do so. The Rama (ibid.) says that if someone calls him to duchen, which turns him into one who is obligated from the Torah to duchen, the obligation overpowers concerns of confusion. Poskim explain (see Yalkut Yosef ibid.) that generally when the kohanim are called, they do not intend for the chazan. One can argue that in shuls with the minhag that the chazan does duchen, the kohen chazan will thus be bound based on the Rama. However, in our shuls, the kohen is called too late, as a kohen who has not begun to approach the duchan before Modim may not do Birkat Kohanim (Shulchan Aruch ibid. 8). Nevertheless, just the fact that you are in a shul which has the minhag for the chazan to duchen is enough to follow the minhag. This is ostensibly so even for someone who has not joined the community in a manner that he should personally adopt all of their minhagim. Still, it would be best for someone like you to avoid being chazan at tefillot that have Birkat Kohanim, which is anyway a practice that many suggest for any kohen (see Birchot Horai 10:7).

This is not a ruling about a specific case but a discussion of the general scenario. We start with the question of a halachic requirement to pay.

This is an example of a person causing damage without doing something that is direct damage (nezek). It is difficult to consider not buckling direct damage one person does (adam hamazik) or to compare it to one of the other Torah-described categories of damage (i.e., damages done by one’s animal, fire, and pit, or matters derived from them – see ch. #1 of Bava Kama). There are another two categories of one causing damage to another. One, called garmi, can be described as semi-direct damage; we pasken that the causer is obligated to pay (Shulchan Aruch, Choshen Mishpat 386:1). The other, gerama, is less direct causation. There is no enforceable compensation for gerama (Bava Kama 60a), but it is prohibited to cause loss in that way (Bava Batra 22b), and there is often a moral obligation to pay (see ibid. 55b). How to determine what is gerama and what is garmi is one of the most complicated questions in Halacha. Factors that may play a role include: whether he did so purposely or accidentally (see Shach, CM 386:6), especially when the damage came from an external source (see Pitchei Choshen, Nezikin 4:(23)); how likely it is that the action will cause damage (Rosh, Bava Kama 9:13); how immediate was the damage (see Sha’ar Mishpat 386:1). 

In this case, many factors favor the passenger if the situation was in a “normal” (although we strongly urge wearing seatbelts) manner. He did not intend to cause damage. The chances of getting caught are small. The damage probably happened well after he got in the car (one can argue that every moment of not putting on the belt is a new affront and view being caught as immediate).

However, there is a stronger reason to exempt the passenger from outright obligation. There are two traffic violations involved here; the policeman could have given two tickets! One (#6706) is by the passenger for not putting on the seatbelt; another (#6705) is by the driver for driving when someone is not buckled in. The “damage” comes based on the “law of the land,” which enables authorities to fine those whom they want to deter from dangerous activities that hurt society. Two people did something illegal – the passenger and the driver. The authorities are interested in teaching both a lesson – BUCKLE UP to save lives or pay money. Your friend directly failed in doing what the law demands of drivers – demanding that people put on their belts. If so, the passenger did not cause the damage, as defined by the law. In some ways, it is like someone getting a ticket for tailgating an improperly slow driver. It is hard to claim that the slow driver is legally responsible for the tailgater dealing with the situation in the wrong way. Here too, the driver could have and did not demand to buckle up.

If the driver did make the demand and the passenger deceived him, he purposely and immorally (as a guest in someone else’s property) endangered the driver. In such a case, if the police knew what happened, they would presumably have penalized only the passenger. It might still not be certain that this is garmi, but many a dayan would obligate the passenger, based on his behavior, and the driver could make that demand.

It would appear that there are contradictory approaches on the idea of withholding requests on Shabbat. The Yerushalmi (Shabbat 15:3) says that one is not allowed to “demand his needs” on Shabbat. In Berachot (5:2), it explains that Havdala in Shemoneh Esrei is at the very beginning of the request section because requests are inappropriate before ending Shabbat. The gemara (Berachot 21a), though, rules that if one began one of the middle berachot on Shabbat, he completes that beracha, as the middle berachot are appropriate and are withheld only to avoid tircha (extra toil) on Shabbat for daveners. So it seems to be a machloket whether the content of requests is appropriate on Shabbat. (Some Rishonim (see Beit Yosef, Orach Chayim 268) say that only the first beracha can be done if started by mistake, because asking for wisdom is a spiritual request. The Shulchan Aruch (OC 268:2) rejects this distinction.)      

However, a distinction in the first Yerushalmi allows the sources to coexist. It raises the question of whether the parts of the third beracha of Birkat Hamazon that contain requests can be recited on Shabbat. Its answer is that it can since it is a tofes (set form of the) beracha. In other words, special requests are problematic, not ones that are part of the normal text. Thus, Chazal did not have to remove Shemoneh Esrei’s middle berachot but decided to do so because of tircha (Aruch Hashulchan, OC 268:3). Therefore, if one accidentally slips into the set Shemoneh Esrei mode, he may finish it. The Midrash Tanchuma (Vayeira 1) does gives a different reason for omitting the middle berachot – thinking about the needs addressed in these berachot can remind one of his problems and make him unduly sad.

We might suggest that requests of the masses are permitted, as they are in the first and last three berachot of Shemoneh Esrei (Shulchan Aruch, OC 112:1). However, the Rivash (512) proves from the fact that the requests in Birkat Hamazon, which apply to the masses (Yerushalayim etc.), would have been forbidden if they had not been part of the set text, that this does not solve the Shabbat problem.

It is unclear the extent to which being set helps. On the one hand, the Rivash explains that Zocherenu L’chayim can be said during Shabbat of Aseret Y’mei Teshuva because it is a set part of Shemoneh Esrei throughout that period. The Ohr Zarua (II:89) similarly justifies Elokai Netzor (full of requests) on Shabbat on these grounds. This is not obvious when one considers that it is somewhat after the Amida and Chazal did not institute it as a required text (Berachot 17a cites it as one Amora’s personal prayer). He says that it is permitted now only because it has become widely accepted, implying that an individual’s set addition would be a problem.

The Rivash (ibid.) discusses Avinu Malkeinu, reasoning that since it is separate from regular tefilla, it should be improper on Shabbat. (On the other hand, he justifies all of the several minhagim on the matter, saying that the halachic issues are not serious enough to change a community minhag.) We should also note that almost all communities recite public requests (e.g., Yekum Purkan), specifically on Shabbat, as well as Mi Shebeirach for the sick (we do add, “Shabbat hi milizok”).

In short, while it is difficult to explain every element of our minhagim on public prayers on Shabbat, the individual should not add his own requests, other than in a case of acute need that cannot be delayed. Your question about peace presents a wonderful opportunity to point out that we have many opportunities. Sim Shalom, which remains in the Shabbat Amida, is a request for peace. Nothing prevents us from taking a little extra time to contemplate ideas that abound in our standard text and cognitively relate them to matters that are on our mind. One should just avoid doing it a manner that makes him sad on Shabbat.        

We will focus mainly on your assumption – that one may add personal thanks in Modim. There is little in the poskim on this specific question, but we can learn from many general relevant sources (find article by R. Chanan Ariel).

Gemarot say that one may add personal requests in Shemoneh Esrei’s middle berachot, especially Shema Koleinu (Avoda Zara 8a; see Shulchan Aruch, Orach Chayim 119:1) but not during the first three and last three berachot (Berachot 34a; see Shulchan Aruch, OC 112:1). The latter are reserved for praise and thanks, respectively. This implies that it is fine to add praises and thanks in those places. In fact, in allowing making communal requests during the berachot, Rabbeinu Tam (cited by Tur, OC 112) says that asking for the needs of the masses is a praise to Hashem, which implies that actual praise is certainly fine.  

However, praises also require caution. The gemara (Berachot 34b; see Shulchan Aruch, OC 113:9) criticizes those who go beyond the set praises of Hashem because they imply that they have mentioned all of Hashem’s greatness. It seems implausible that it could always be forbidden to praise and/or thank Hashem, so when is it? The Beit Yosef (OC 113) cites the Ra’ah and Rabbeinu Yona as saying that one may not add adjectives describing Hashem but may add mention of good things He did. Rabbeinu Yona also distinguishes between things said at the end of berachot and those in the middle of berachot. The latter stand alone and are permitted. It is unclear from the corresponding Shulchan Aruch if he accepts these distinctions.

There is a machloket in the sources and minhagim about adding piyutim to tefilla at certain times. The Shulchan Aruch (OC 68:1) opposes it, apparently because it is an interruption, changes the berachot’s length, and encourages talking (see Tur ad loc.). The Rama supports it, but the minhag nowadays is to do so only on Yamim Noraim. There was also controversy about Aseret Y’mei Teshuva additions (Zochreinu, etc.) to tefilla (see Beit Yosef, OC 112), and there the minhag is to say them. One might distinguish, though, between set sayings that are accepted by Klal Yisrael and personal ones.

We have written (Living the Halachic Process, vol. II, A-1) that it is permitted and positive to thank Hashem but that it can be problematic to do so in a manner that makes it appear like a set beracha. Attaching appropriate statements to an existing beracha, on the one hand, makes it unlikely for there to be an issue of beracha l’vatatala (see Mishna Berura 108:38). On the other hand, changes in the content can be more problematic (See Berachot 40b; Shut HaRambam 254).

We summarize and suggest as follows. Since the lack of sources and apparent minhag is to not add personal thanks during Modim, then even though it is probably halachically permitted, we do not suggest it when other options exist. Before Elokai Netzor and during Shema Koleinu, one can say anything appropriate, and while that is classically for requests, it should be fine to thank Hashem as well. Realize that even the middle, “request” berachot include praise. Therefore, the following example of an addition would seem ideal: “Bless my grandchild, for whose birth I am so grateful to You, with a wonderful life.” (See a similar idea in Yaskil Avdi, vol. VIII, p. 169.)

Regarding Shabbat, there are two reasons for requests, such as the middle berachot of Shemoneh Esrei. The Yerushalmi (Shabbat 15:3) says that one should not make personal requests on a day that one must not be focused on his needs. The gemara (Berachot 21b) says that we do not want the toil of a long tefilla. Apparently, some combination of the two ideas is true. [We will discuss the issue next week.] If you want to give only thanks in Modim or before Elokai Netzor, this is not a problem on Shabbat. Incorporating a request (see above) is likely inappropriate on Shabbat.