Ask the Rov: During Chol Hamoed, I found a bag of pretzels under the seat of my car. What should I do?
By Rabbi Chaim Hillel Raskin – Rov of Anash in Petach Tikvah
Shulchan Aruch rules that if one finds chametz in their possession during Chol Hamoed Pesach, he should take it out and burn it. If the chametz amounts to a kezayis, one recites the bracha of al biur chametz. Although he already recited this bracha before beginning bedikas chametz, this only covers the destruction of the chametz found during the search and other chametz he was aware of at that time, which is the culmination of the same mitzva. But once that mitzva has been completed, a new bracha must be recited on a subsequent destruction of chametz.1
If the chametz is found on Shabbos or yom tov, some hold that it is muktza since it’s useless and may not be moved with one’s hands. There isn’t either and allowance to burn it on yom tov since it doesn’t have a food preparation purpose (ochel nefesh). One must instead cover it securely to hide it from view, taking care not to move the chametz, and wait to burn it until after yom tov.2 Even once Pesach is over, that chametz must still be burned without a bracha.3
Contemporary poskim note that in the present age, when people sell their chametz before Pesach, the halacha would be different. Since the mechiras chametz includes all of a person’s chametz wherever it may be, the discovered chametz belongs to the goy as well (unless it was intentionally excluded from the sale (to eat before Pesach) or it was ch”v purchased on Pesach).
Thus, if one finds such chametz, he should move it to the area that has been closed off and designated for the sold chametz. 4 Although this chametz already belongs to the goy, it must still be closed off like all the other sold chametz so that no one mistakenly eats from it.5 (Chametz found outside of one’s property should not be lifted on Pesach, as it may constitute an acquisition of the chametz.6)
During Pesach, it is forbidden to touch any chametz, even belonging to a non-Jew, as a decree to safeguard against forgetting the prohibition and mistakenly eating it. Therefore, the chametz that one finds should be pushed indirectly, with a stick or broom, into the closed-off area.7
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From The Weekly Farbrengen by Merkaz Anash
Is there any knas for this? Like not being able to use that chometz after Pesach?