הלכה על פסחים 2:1

Although the Gemara makes clear that one may benefit from chametz that is no longer ra’ui l’achilat kelev, the Rishonim debate the permissibility of actually eating it. The Rosh (Pesachim 2:1) cites opinions that one may even eat such chametz. He himself rejects this view, however, and rules that one may only benefit from such chametz (as explicitly stated in the Gemara); by eating it, one would “elevate” the chametz (achsheveih) from a non-food item to a food item. The basis for this is the Gemara’s (Shevuot 24b) ruling that if one swears not to eat an inedible item and subsequently eats it, he has then violated his oath because he has “elevated” that item to the status of food by consuming it. The Shulchan Aruch (O.C. 442:9; see Mishnah Berurah 442:43) rules in accordance with the Rosh.