We will begin by examining the purposes and mechanisms of the different bituls.
The Torah forbids possession of chametz on Pesach[2] and mandates its removal before Pesach.[3] To facilitate this, we search for chametz the night before Pesach[4] and physically “destroy” the leftovers (bi’ur chametz) the next day. The gemara[5] states that the Rabbis instituted that one perform bitul chametz after he has done bedikat chametz. The gemara explains that this bitul is required out of concern that one might find some tasty chametz on Pesach, which would be problematic if one had not done bitul.[6] This is the bitul chametz recited after bedikat chametz at night.[7]
The gemara does not mention the bitul’s text, and slightly varied versions exist.[8] The consensus, however, is that the bitul applies to chametz that is unknown to the declarer at the time of the bitul. One reason to exclude known chametz from the bitul is that some of one’s chametz is slated to be eaten during the next half day; a statement that this chametz is worthless and ownerless is therefore disingenuous.[9] In addition, the complete fulfillment of bi’ur chametz is accomplished with one’s own chametz, and one therefore wants the chametz he is to burn the next day to remain in his ownership.[10]
Daytime bitul is a post-Talmudic minhag[11] designed to deal with the possibility that some of the chametz that was purposely left over was neither eaten nor destroyed.[12] According to most poskim, this bitul is done after the bi’ur chametz. It therefore uses inclusive terminology;[13] one is mevatel all known chametz in addition to unknown chametz. This can even include chametz that was thrown into the fire but was insufficiently destroyed.[14]
If one uses the daytime text at night, nullifying even known chametz, it will ostensibly impact even that chametz that he plans to eat or burn the next day. Is this problematic?
First, we should consider whether this bitul takes effect at all, considering that it is done in a mistaken fashion. If one reads the words of bitul without understanding what the bitul is supposed to accomplish, the bitul is ineffective.[15] However, one does not need to understand every word; a reasonable level of understanding of the overall content of what his words are accomplishing is sufficient.[16] Arguably, one who read the morning version instead of the night version might not have understood what he was saying. Regarding the extra words of inclusiveness that exist in the daytime bitul, he may have intended for the more limited nullification and not for the words that included known chametz, in which case it did not take effect on that which he did not mean to say. If he understood and meant what he read but did not remember the relevant halachot, we can consider the concept that declaration of hefker (declaring an object ownerless) based on false assumptions is ineffective,[17] and the same might also be true regarding bitul chametz.[18] It is a good question whether including extra chametz that one ordinarily nullifies only the next morning rises to the level of mistake that disqualifies the declaration in their regard. In any case, the mistake regarding the additional chametz should not disqualify the bitul regarding the chametz for which it is normally intended.
Now we will analyze the consequences of the possibility that the bitul did, in fact, take effect on all of the chametz. First, we must examine what the bitul chametz accomplishes. According to Tosafot,[19] bitul makes chametz ownerless (hefker). According to this view, assuming that no one hears the owner’s mistaken declaration and takes the still-desired chametz, the owner can eat all of the nullified chametz either as is or by first reacquiring it. (If it is in his house, no action is necessary to reacquire it.[20]) Regarding wanting the chametz to be his so that he will be burning his own chametz, one can likewise easily reacquire it. Reacquiring it might be more critical in order to facilitate mechirat chametz (which rabbis perform the next morning), as one can sell only that which he owns.
According to Rashi,[21] bitul is not based on hefker, but is instead a special “mental destruction” of chametz, which the Torah indicated as significant with regard to one’s chametz. This does not affect one’s ability to eat the chametz he desires before the time of bi’ur chametz. Moreover, it probably also does not impact on one’s ability to sell the chametz to a non-Jew. In fact, it is likely that the act of sale of food that one put aside in a special place for that purpose might undo the bitul of that chametz, as one demonstrates that his chametz is at that time still of at least theoretical value for him (as the non-Jew is nominally willing to pay for it). Undoing the bitul is not a problem, as he will presumably perform another bitul the next morning anyway, and that later bitul will work in the same manner as it does in regular situations. It is possible that the bi’ur chametz for chametz set aside after such a bitul would be considered bi’ur of chametz that is not one’s own, and the mistaken declaration could thus in theory be negatively impactful.[22] However, as noted above, bitul without intent, and probably even by mistake, is fundamentally not valid.[23]
While most likely unnecessary and not clearly effective, it would be a good idea[24] for a person in this situation to declare that he reverses his declaration regarding the chametz he is aware of.