Deuteronomy 20:14-18

14but the women, and the little ones, and the cattle, and all that is in the city, even all the spoil thereof, shalt thou take for a prey unto thyself; and thou shalt eat the spoil of thine enemies, which the LORD thy God hath given thee.

15Thus shalt thou do unto all the cities which are very far off from thee, which are not of the cities of these nations.

16But of the cities of these peoples, which the LORD thy God giveth thee for an inheritance, thou shalt save alive nothing that breatheth:

17but thou shalt utterly destroy them; the Hittite, and the Amorite, the Canaanite, and the Perizzite, the Hivite, and the Jebusite; as the LORD thy God hath commanded thee:

18that they teach you not to do after all their abominations, which they have done unto their gods; so should ye sin against the LORD your God.