Midrash su Levitico 20:15

1) (Vayikra 20:15) ("And if a man gives his lying to a beast, he shall be put to death, and the beast you shall kill.") "And a man": to exclude a minor. "who gives his lying to a beast" — whether full grown or not. "he shall be put to death": by stoning. You say by stoning, but perhaps it is by one of the other death penalties in the Torah; it is, therefore, written "and the beast you shall kill," and, elsewhere (Devarim 13:10) "You shall surely kill him." Just as there, by stoning; so, here, by stoning.

(Exodus 22:18) "Whoever lies with a beast shall be put to death": What is the intent of this? It is written (Leviticus 20:15) "And a man who cohabits with a beast shall be put to death" — by stoning. You say by stoning, but perhaps, by one of the other death penalties in Scripture? It is, therefore, written (Ibid.) "and the beast shall you kill." It is written here "kill," and elsewhere (Devarim 13:10) "kill." Just as there, stoning (is indicated), so, here, stoning. We have heard the penalty. Whence is the exhortation (derived)? From (Leviticus 18:23) "And you shall not cohabit with any beast." This tells me only of the punishment and the exhortation for the active agent. Whence do we derive the punishment for the passive agent? From (our verse) "Whoever lies with a beast shall be put to death." Scripture (hereby) equated the passive agent with the active one. Just as the second is to be stoned, so, the first. We have heard the punishment. Whence the exhortation (for the passive agent)? It is, therefore, written (Devarim 23:18) "and there shall not be a (male) harlot among the children of Israel," and (I Kings 14:24) "And there was also a (male) harlot in the land. They did according to all the abominations of the nations which the L rd drove out."