The Behemoth upon a thousand hills (Ps. l. 10), God created them male
and female, but had they been allowed to propagate they would have
destroyed the whole world. What did He do? He castrated the male and
spayed the female, and then preserved them that they might serve for the
righteous at the Messianic banquet; as it is said (Job xl. 16), "His
strength is in his loins (i.e., the male), and his force in the navel of
his belly" (i.e., the female).
THE TALMUD, _Bava Bathra_, fol. 74, col. 2.