Rashi on Leviticus 17:15/רש"י על ויקרא י״ז:ט״ו

1אשר תאכל נבלה וטרפה [AND EVERY SOUL] THAT EATETH CARRION, OR THAT WHICH WAS TORN … [HE SHALL BOTH WASH HIS GARMENTS AND LAVE HIMSELF IN WATER] — Scripture is here speaking of the carrion of a clean bird which causes uncleanness only during the time it passes through the gullet (lit., it is being swallowed in the gullet) and what Scripture teaches you here is that it makes one unclean by eating of it [but it does not defile one by touching it]. The טרפה mentioned here (though being superfluous since a טרפה which died) is of course also a נבלה and thus causes uncleanness just as any other נבלה is mentioned only for the sake of the correct interpretation of the word נבלה. For thus we learn (in Sifra): One might think that the carrion of an unclean bird causes uncleanness in the moment it passes through the gullet! Scripture therefore adds the word טרפה to intimate that this law of נבלה applies only to that class of birds among which טרפה is possible, thus excluding unclean birds for in their class a רפה‎ט can never occur (Sifra, Acharei Mot, Chapter 12 7; Zevachim 69b).