Of the different periods of national mourning leading up to Tisha B’Av, the one with the lowest level of intensity is the first part of Bein HaMetzarim (the Three Weeks), from the 17th of Tammuz until Rosh Chodesh Av. No restrictions are mentioned in the gemara regarding this period. Even the well-known restriction of marriage during the Three Weeks[2] is post-Talmudic before Rosh Chodesh, and Sephardim do not even subscribe to this restriction.[3]
Questions regarding customs of this period of national mourning are difficult to analyze halachically. On the one hand, the more religiously significant a particular event is, the more we would like it to take place in the nicest way possible. It is for this reason that it is acceptable and even preferable to eat meat at a siyum, even during the Nine Days when Ashkenazim usually do not eat meat.[4] On the other hand, the stronger an event’s joyous character, the more likely it is that the celebration itself is significant enough to be forbidden during this period, even if it is a mitzva and even if it is celebrated without extra flourishes. Therefore, it is forbidden to get married even without a celebratory meal.[5]
A chanukat habayit is an expression of joy and gratitude over moving into a home that is new for its inhabitants. There are restrictions regarding joyful practices involving the home. During the Nine Days (and perhaps during the Three Weeks[6]) it is forbidden to perform non-essential beautification work on a home.[7] Along the same lines, we avoid entering a new home during this time unless this is necessary so as to avoid a significant loss.[8] Since one may enter a new home before the Nine Days,[9] the problem presented by a chanukat habayit is only from the perspective of the added activities of the celebration.
The nature of the celebration is relevant here. Many Sephardim have the minhag to perform a ceremony, with specific Torah texts recited, on the day that they enter the house; some will not even sleep in the house before doing so.[10] Here, the words of Torah are the main component of the ceremony, whereas the accompanying festivities are only ancillary; such an event is certainly permitted.
A further reason for leniency is the fact that many consider a chanukat habayit in Israel to be a celebration of the fulfillment of the mitzva of yishuv Eretz Yisrael, which then allows for the leniencies connected to a seudat mitzva. Indeed, the Torah[11] views inaugurating a home as significant enough to allow someone to leave the battlefront, but only in Eretz Yisrael.[12] While one can distinguish between actually living in the house in Eretz Yisrael and the celebration over the building of a home there, the B’er Sheva[13] says that even the celebration over the building of a home is a seudat mitzva in Eretz Yisrael (but not abroad). While it is not simple to allow this celebration during the Nine Days,[14] the chanukat habayit per se is permitted before Rosh Chodesh.
If the celebration is not on the actual day that one enters the home, there are two reasons to be more stringent. One is that the level of the mitzva to perform such a celebration may be lower when it is not on the same day. The other is that if one is already delaying the celebration, it makes more sense to delay further until after Tisha B’Av. That being said, since there is no classical source to forbid a chanukat habayit before the Nine Days, if one has good reasons to do it specifically at that time, we would not forbid it. (We would urge one in this situation to remember to put a stress on divrei Torah and thanks to HaShem.)
Keep in mind that certain possible parts of the celebration may pose a problem. Some people ordinarily make Shehecheyanu as they enter their new home, which is problematic during the Three Weeks; we do not say “Shehecheyanu … lazeman hazeh” during the Three Weeks because “this time” is a sad one.[15] However, we anyway maintain[16] that this is not the correct beracha to make for an Ashkenazi family moving in to a new home. (Yalkut Yosef,[17] based on the Shulchan Aruch,[18] writes that Shehecheyanu is the correct beracha. He is therefore opposed to having a full-scope chanukat habayit during this time, as Shehecheyanu would be included. On the other hand, he allows a meal with ten people reciting the appropriate passages according to one’s minhag.)
In addition, it is accepted not to play music or dance during the Three Weeks.[19] Therefore, it is proper to forgo music[20] or dancing at the celebration at a chanukat habayit at this time, since those are not an integral part of such an event.[21]