A Tale of Two ‘Bitul’s (nullifications)
After BC is complete, one should recite his first bitul. It is essential that he understand the words of the bitul; this is a declaration, not a prayer! The original version, found in the Siddur or Haggada, is in Aramaic, because that was the vernacular. If one does not understand Aramaic, he should recite it in his mother-tongue. The declaration states (English translation from Artscroll Siddur, p. 655): “Any chametz or leaven that is in my possession which I have not seen, have not removed and do not know about, should be annulled and become ownerless, like dust of the earth.” Note that any known chametz is not being nullified at this point, because: a) one wishes to still eat some chametz, and b) one wishes to burn chametz the next day. The second bitul should be done the next morning. When? Some time after he has finished eating the remaining chametz, and after he has burned (‘biur’) whatever he wishes to burn, but before the final deadline for burning. (Reason: If he nullifies before the ‘biur’, then he cannot fulfill the mitzvah of burning his chametz! If he waits until after the deadline has passed, the Torah will have removed it from his possession automatically, and it is no longer his to nullify!) In the version of the second bitul, he changes the wording to: “… whether I have recognized it or not, whether I have seen it or not, whether I have removed it or not…” This covers all of his chametz!
Question: Why is it necessary to do a bitul in the evening at all, if he will do an even more inclusive bitul the next morning anyway?
Answer: This is just a precaution, in case he should forget to do the second bitul. Now, while he is still involved with BC, he is sure to remember to do bitul. The next day, however, there is more of a chance he may forget.
Question: May one person nullify another person’s chametz on his behalf?
Answer: That is a controversial question. Without express appointment to do so, definitely not; with appointment, as a last resort. (Note: Even if the homeowner appointed someone to do BC as his agent, that does not implicate appointment for bitul, which is a totally different transaction.) It is far preferable for a person to do his own bitul – even if he is not at the location of the chametz or its burning. If one cannot - or will not - do the bitul himself, his wife may do it – even if he did not explicitly appoint her to do so.
General question: Why does halacha necessitate bitul altogether, if one does a thorough BC and burns any found or remaining chametz?
Answer: One might think that the bitul is to account for any chametz one inadvertently misses in his search, so that he should not be in violation of BYBY (i.e. owning chametz on Pesach.) I recently learned the explanation of Rabbeinu Nissim (Ra”N) in his commentary on the Talmud, who addresses this question, and gives a different reason. He writes that, in fact, that the Torah would not penalize a person were he to miss some chametz in his search, for as long as he conducts the search in the way prescribed by halacha, he may rely on the ‘chazaka’ (resumption) that there is none remaining. If he should find some, even on Pesach itself, he may simply destroy it (or, on Yom Tov, place a vessel over it and burn it after Yom Tov is over), and he has no transgression! The only thing the Rabbis were afraid of was that that were he to find a nice-looking piece of chametz, and hesitate in his mind about whether or not to burn it, then at that moment, he would be in violation of BYBY! By nullifying all of his chametz in advance, he pre-empts even that remote possibility.