‘A Loaf Went Moldy And…Unfit For Human Consumption’
The Gemara cites two baraisos which state that one is obligated to dispose of one’s bread before Pesach even if it is moldy. The first baraisa explains that moldy bread may not be kept on Pesach because it is capable of leavening other breads (and therefore has significance). The second baraisa states that one is only obligated to dispose of moldy bread if it is fit for animal consumption. However, if it has spoiled to the extent that even a dog won’t eat it, it is rendered insignificant and as such may be kept in one’s house over Pesach (for it is considered as mere dust).
Some Redeeming Value
The Ran (ad loc.) cites R. Shimon (Avoda Zara 67b), who derives from a pasuk that forbidden foods unfit for human consumption are not forbidden by the Torah. In light of this, the Ran asks why the baraisa requires one to dispose of spoiled bread which is unfit for human consumption.
The Ran answers that moldy bread is more significant than other rotting foods because it can be used as a leavening agent for dough, as the first baraisa states. (The Ran supports this logic with a Gemara [Betzah 7b] that seems to say that the reason the Torah forbids eating se’or [sourdough] on Pesach is because it is used as a leavening agent and is therefore significant despite being inedible.)
A Leavening Agent?
Rabad (to Rambam, Hilchos Chametz U’Matzah 1:2) has another approach. He says that the baraisa is not referring to an ordinary loaf of bread but rather to a block of se’or. The baraisa teaches that se’or must be disposed of even if it is unfit for a dog because of its significance as a leavening agent. (We find similarly in a Tosefta to the first chapter of Tractate Betzah: When is it referred to as se’or? When it is unfit for consumption by a dog.)
The second baraisa, says Rabad, teaches that ordinary bread must be disposed of if it is spoiled and unfit for human consumption. However, in contrast to se’or, moldy bread must at least be fit for animal consumption (since it does not have the significance of a leavening agent). Rabad evidently does not consider ordinary bread to be a leavening agent, as does the Ran.
The Minchas Baruch (siman 35) comments that Rabad seemingly does not rule in accordance with R. Shimon (cited by the Ran above), for he prohibits moldy chametz which is unfit for human consumption (even though it is not a leavening agent). Apparently, he holds that all forbidden foods remain prohibited, even if they are rotting and unfit for human consumption.
Alternatively, the Gaon Rav Chaim Ozer Grodzinski (Achiezer vol. 3, 5:2) explains that Rabad actually does follow R. Shimon’s ruling and permits forbidden foods which have spoiled and are unfit for human consumption. However, the issur of owning chametz – bal yera’eh – is an exception and applies even to spoiled food because it is not an issur that relates only to foods that are prohibited to be eaten.