Commento su Deuteronomio 14:12

וזה אשר לא תאכלו מהם BUT THESE ARE THEY WHICH YOU MAY NOT EAT — This again is intended to forbid as food the bird that is slaughtered in the case of a leper (Sifrei Devarim 103:1-2; Kiddushin 57a).

וזה אשר לא תאכלו, “this is the type of bird you may not eat;” this includes birds which have undergone ritual slaughter. The following had to be stated explicitly, as once no longer alive, such birds are susceptible to ritual impurity. One might have thought since the ritual impurity that had left the person stricken with tzoraat had been transferred to his offering, that offering had become contaminated. The Torah therefore indicates that this is not the case.

This prohibits the slaughtered bird [offered by the metzora]. Apparently it is expounded this way because the phrase, “This is what you may not eat,” is apparently superfluous. For below it is written (v. 19), “And all flying creeping creatures are ritually unclean for you, they may not be eaten.” Rather, the verse here intends to forbid the bird that is slaughtered by the metzora. The Gemora (Kiddushin 57a) asks, “I would say the opposite — forbid the [metzora’s] released bird and permit the slaughtered bird.” And the Gemora answers, “The Torah does not say to release the bird if eventually it may cause a liability” — that a person might unknowingly sin by taking and eating it. Re”m asks: If [this reasoning is] so, then why is the phrase, “[You may eat] any pure bird,” needed to permit the released bird? Re”m answers: The explanation, “Any pure bird — this permits the released bird,” is only an asmachta [a loose interpretation]. Also Rashi there says this explicitly (ibid.).