Leftovers

A student asked:

After pesach you find Chametz in your house, and you didn’t know it was there all of pesach are you allowed to eat it or to have to sell it or throw it out?

The student touches on an important rule here. Biblically, we are not allowed to eat or own chametz on Pesach, but מדרבנן, Chametz sheavar alav hapesach - chametz that was owned by a Jew over pesach is prohibited as well. Therefore, you would think that the answer to your question is that you have to throw out any chametz that you accidentally had over Pesach.

There are two reasons why this may not be so. First, every Jew, on the morning of erev Pesach, does "ביטול חמץ" - the nullification of the chametz. In it we state our desire to be rid of any chametz we may own, whether we know about it or not, which has the effect of making it not ours. (There is a famous machlokes between Rashi and Tosfos as to the mechanics of how this works, but that is beyond the scope of this post.)

Additionally, most people have the custom of selling their chametz to a non-Jew for the duration of the holiday. If the chametz you find is in a place you didn't expect it, and thus didn't sell this may not help.

This is all on top of the thorough cleaning job we all do in anticipation of Pesach, so you see that we take multiple precautions to ensure that we do not violate the Biblical prohibition of owning chametz on Pesach. Therefore, the item you find afterward may well not have been yours "illegally" on Pesach, and may not run afoul of the rules of חמץ שעבר עליו הפסח. For an actual ruling, please see your personal Halachik authority.

The baalei mussar explain that chametz on Pesach, and our effort to eradicate it is representative of whatever bad midos we have in ourselves. The extraordinary pains taken - halachik and personal (I myself should probably be doing something else now) - to ensure that no chametz remains under our care is an important message to us as we try to do the appropriate introspection before the chag.

Wishing everyone a chag kasher v'sameach.