If one failed to search for chametz on 14 nissan, one has the obligation to search the next day. And again, if one failed, one has to search, even on the festival itself and during pesach (from our heritage eliyahu kitov ). Knowing that this year, our pesach begins on Friday night, if one failed to search on Thursday night and all of Friday, should one search and burn the chametz on Shabbat?
This can be similar to the situation of Pesach 5765, in which Erev Pesach was Shabbos and there was chometz (such as the rolls for lechem mishna) that could not have been destroyed on Friday. The chometz is muktzah and must be covered until after Shabbos and then burned. Note that moving it or covering it are subject to the rules of muktzah which is not the subject of this question. This is also the situation in which one finds chometz during a regular Pesach during any time that biur is forbidden (such as Yom Tov).
There are actually those who say that this depends on the contract that one used to sell the chametz before Pesach. I will summarize that situation after the initial quote.
HaShoneh Halachos emails include two halachos per day, seven days a week (emails for Shabbos and Yom Tov are sent in advance). Material is based upon the Kitzur Shulchan Aruch, with occasional elucidation from the Mishnah Brurah abd other sources. The text is not a direct translation but a paraphrase into easy-to-read, conversational English.
111:17 If one found chometz on yom tov, on Shabbos of chol hamoed, or on Shabbos that is erev Pesach – on any of which he would not be permitted to handle the chometz because it is muktzeh – he should cover it with a vessel until after yom tov or Shabbos, then burn it. If it was found on the last days of yom tov so that after yom tov, Pesach will be over, he burns it without a bracha, even if it is more than a k’zayis.
There are those who say that the chametz can be put in with the Chametz that had previously been sold and the chatzer would be koneh it. Others say the chatzer would not be koneh it and it must be destroyed. There are those who say that the contract to sell the chametz would have included the chametz that was found, and as such it belongs to the non-Jew to whom all the chametz in the house was sold. As a result, it cannot be destroyed as that would be theft from the non-Jew. Others say it can be destroyed as the non-Jew would not be makpid on its destruction and the Jew would be purchasing the entire chametz (including what had been destroyed) back at the original price.
In any case, it must be handled in accord with the laws of muktzah and covered until after Shabbos or Yom Tov. If necessary it can be kicked into a corner with a shinui before being covered.
Q: Last year someone discovered chametz in his house on Pesach. He asked whether he should put it away with the rest of the chametz that he sold to the gentile so the gentile would acquire it, or must he destroy it?
A: The method of acquisition that you describe is called kinyan chatzer and involves one’s property acquiring possessions on his behalf. There is a debate regarding the efficacy of a kinyan chatzer for a gentile. The mechanism of this proprietary act is that one’s property works as his agent and the halachic principle of agency does not exist for a gentile (see Ketzos 194:3 and Nesivos, introduction to 200). In this circumstance, when one discovers chametz after it is prohibited, it is not possible to sell it, and declaring it ownerless or throwing it in the trash would not be effective. The chametz must be destroyed (O.C. 446:1), and preferably it should be burned (M.B. 445:6).
The truth is, however, that nowadays, even though the chametz was not placed where the chametz that was sold to the gentile is stored, it was, nevertheless, sold, and belongs to the gentile. The reason is that the contract that one signs to sell his chametz to the gentile includes even chametz that is not stored in the designated area. Therefore, the chametz that is found should be placed where the rest of the sold chametz is stored (since it is prohibited to leave the chametz in an area not rented to the gentile out of concern that one will inadvertently eat it — O.C. 440:2). On Yom Tov, when chametz is muktzeh, it should be pushed into that area in an unusual manner.
Moreover there are authorities (Mikra’ei Kodesh, Pesach 1:74) who write that nowadays when people sell all of their chametz it is prohibited to take the forgotten chametz to burn it. The reason is that if one were to physically take the chametz to burn it he would actively violate the prohibition against owning chametz, because he thus becomes a thief and is responsible to return the chametz to the gentile who purchased it (see Magen Avraham 586:5, which states that one who steals chametz from a gentile is responsible for it and it is considered his chametz by virtue of that responsibility). Although his intent is not to steal in order to assume ownership, nevertheless, even taking another’s possession with the intent to destroy it is categorized as theft (B.K. 98a).
Others contend that although it would seem that one may not destroy the chametz, since it belongs to the gentile, he is permitted to burn it. Although the sale of the chametz is certainly valid and binding and one may not cancel that sale, nevertheless the gentile’s intent when purchasing the chametz is to assist the Jews who plan to repurchase it. Whatever money the gentile spent to purchase the chametz will be refunded after Pesach when he resells it to the Jews; if a piece of chametz is burned, it will not affect that sale. Since the gentile is not particular whether a piece is burned or not, it is not considered theft for a Jew who finds it to take it to burn. Therefore, according to this opinion, someone who does not want to rely on the sale of chametz for actual chametz may burn chametz that he finds on Pesach (Shevet Halevi 9:116; Kisei Mishpat 187).