Halakhah for Exodus 12:19

A similar rule applies to all forbidden foods – as the Gemara (Avodah Zarah 67b-68a) states, the Torah forbids only food that is fit for human consumption. Regarding Pesach, however, we are stricter, requiring that the chametz be unworthy even for canine consumption.¹This is consistent with Halachah’s unusually strict overall approach to chametz on Pesach, which manifests itself in such laws as the prohibition to own chametz and the impossibility of nullifying it in a mixture. The Ran (13b in the pages of the Rif s.v. Tanu Rabbanan) and the Magen Avraham (442:14) explain that chametz that is fit for canine consumption has the potential to ferment bread. Hence, it is similar to sourdough, which the Torah (Shemot 12:19) specifically forbids for Pesach consumption.

And this commandment is practiced in every place and at all times by males and females. And one who transgresses it and does not dispose of [his chamets], has violated the commandment of 'you shall dispose of it.' And if there is chamets in his dwellings, he also transgresses a negative commandment - as it stated (Exodus 12:19), "leaven is not to be found in your homes." But we do not administer lashes for this negative commandment, if he has not done an act - as it is the law that we do not administer lashes for a negative commandment that does not have an act [involved] with it.

That chamets not be found in our possession on Pesach: That chamets not be found in our possession on all the days of Pesach, as it is stated (Exodus 12:19), "Seven days shall leaven not be found in all of your homes." And our Sages, may their memory be blessed, elucidated (Pesachim 5b) that it is not specifically one's home, but rather anything that is in his possession; and not specifically leaven which makes rise, but the same is true of [any grain product] that has risen - as leaven and leavened grain products are one [and the same] concerning the matter of its prohibition (Beitzah 7b).