Midrash su Levitico 7:24

5) (Vayikra 7:24) ("And the cheilev of a [beast that is] neveilah (carrion) or the cheilev of a treifah ("torn" animal) may be used for all service, but you shall not eat it.") Scripture here speaks of the neveilah of a clean (kosher) animal. (i.e., The cheilev of a kosher animal may be used for all service for it is distinct from its flesh and is not subject to neveilah-tumah, as opposed to the cheilev of an unkosher animal, which is not distinct from its flesh, and both are subject to neveilah-tumah). I might think that the neveilah of an unclean animal is intended, and that this follows by induction, viz.: There is absence of (the kareth of) cheilev and there is absence of (the tumah of) neveilah. It stands to reason that the absence of neveilah-tumah obtains with an unclean animal just as the absence of cheilev-kareth obtains only with an unclean animal. Or go in this direction: There is absence (of neveilah-tumah) where there is cheilev (our instance), and there is absence (of neveilah-tumah) where there is shechitah, (i.e., Just as we find that the latter obtains only with a clean (kosher) animal, (i.e., If an unclean animal is slaughtered through shechitah, neveilah-tumah still obtains), so, the former, (our instance), obtains only with a clean animal. (We now find ourselves in a predicament:) When you go in one direction, only a clean beast is being spoken of. When you go in the other direction, only an unclean beast is spoken of. It is, therefore, written (in the same context as "neveilah"), "treifah" — This excludes an unclean beast, where treifah does not obtain.

6) The implication (of "treifah") is that I exclude (from permission to use the cheilev of a neveilah) an unclean beast, where treifah does not obtain, and that I include (for such permission) a clean animal (as opposed to "beast") where treifah does obtain. It is, therefore, (to negate this,) written "cheilev … you shall not eat" — The cheilev that was forbidden to be eaten, (that of a clean beast,) is permitted (for use). The cheilev of a clean animal, that was permitted to be eaten, is excluded (from use).

7) (Vayikra 7:24) "lo tochluhu": I might think this means that he shall not feed it to others (non-Jews). It is, therefore, written (Vayikra 7:24) "ve'achol" — You may feed it to others. But perhaps "ve'achol" signifies that cheilev from which benefit may be derived is clean (of neveilah-tumah and may be used for all service), but the cheilev of an ox that was stoned, and that of an eglah arufah (the heifer of the broken neck, Devarim 21:1-9, [if it died before its mitzvah was performed]), from which benefit may not be derived, is not clean (of neveilah-tumah). It is, therefore, written (Devarim 21:9) (the redundant) "and the cheilev … and the cheilev" (to include the cheilev of the foregoing as permitted for all use).