Midrash su Levitico 26:27

Exodus 21:28) "the ox shall be stoned and its flesh shall not be eaten": Why is this stated? From "the ox shall be stoned," do I not know that its flesh is forbidden? (It is neveilah [carcass].) But (the meaning is that) if the ox were taken out to be stoned, and its owner intervened and slaughtered it, its flesh may not be eaten. This tells me only of eating. Whence do I derive that it is even forbidden to derive benefit from it? __ Do you ask? If follows a fortiori, viz.: If it is forbidden to derive benefit from eglah arufah, (viz. Devarim 21:1-9) which atones for the spilling of blood, how much more so is it forbidden to derive benefit from a stoned ox, which is itself a spiller of blood! __ But reverse it, viz.: If it were permitted to derive benefit from a stoned ox, which is a spiller of blood, how much more so would it be permitted to derive benefit from an eglah arufah, which atones for the spiller of blood! It is, therefore, written (Devarim 21:4) "and they shall break there the neck of the heifer in the river-bed" (from which it is derived [hermeneutically] that benefit may not be derived from it.) I have reasoned and reversed. The reversal has been nullified and I have returned to the original a fortiori deduction, viz.: If it is forbidden to derive benefit from eglah arufah, which atones for the spiller of blood, how much more so is it forbidden to derive benefit from a stoned ox, which is itself a spiller of blood. Rebbi says: If it is forbidden to derive benefit from the burnt bullocks and the burnt he-goats, which do not come to atone for the world (viz. Leviticus 26:27), how much more so is it forbidden to derive benefit from eglah arufah, which does come to atone for the world! This tells me only of its flesh (i.e., that benefit may not be derived from the flesh of an ox that killed, which was slaughtered after judgment had been passed upon it.) Whence do I derive (the same for) its skin? R. Yishmael was wont to say: It follows a fortiori, viz.: If the skin of a sin-offering, whose flesh is permitted in its slaughtering, is forbidden (in the derivation of benefit) in its death, then an ox to be stoned, whose flesh is forbidden in its slaughtering, how much more so should its skin be forbidden in its death! __ (No,) this is refuted by an ox which has become tamei, which, although its flesh is forbidden in its slaughtering, its skin is permitted in its death. One of the disciples of R. Yishmael said: This may be true of an ox which has become tamei, from which benefit may be derived, for which reason its skin is permitted in its death, as opposed to an ox to be stoned, which, since benefit is forbidden to be derived therefrom, its skin is to be forbidden in its death.