Deuteronomy 20:15

12 If it will make no peace with you, but will make war against you, then you shall besiege it:

13 and when Yahweh your God delivers it into your hand, you shall strike every male of it with the edge of the sword:

14 but the women, and the little ones, and the cattle, and all that is in the city, even all the spoil of it, shall you take for a prey to yourself; and you shall eat the spoil of your enemies, which Yahweh your God has given you.

15 Thus shall you do to all the cities which are very far off from you, which are not of the cities of these nations.

16 But of the cities of these peoples, that Yahweh your God gives you for an inheritance, you shall save alive nothing that breathes;

17 but you shall utterly destroy them: the Hittite, and the Amorite, the Canaanite, and the Perizzite, the Hivite, and the Jebusite; as Yahweh your God has commanded you;

18 that they not teach you to do after all their abominations, which they have done to their gods; so would you sin against Yahweh your God.