R. Yishmael rejoined: I derive "You shall not allow to live" from "You shall not allow to live," and you answer me from "You shall not allow to live" to "it shall not live!" R. Yossi Haglili says: It is written here "A witch you shall not allow to live," and (Ibid. 18) "Whoever lives with a beast shall be put to death." They are juxtaposed to teach that just as the second (is killed) by stoning, so, the first.
Yishmael Rejoined I Derive You Shall Not Allow to Live
Mekhilta Tractate Nezikin 17:16