Deuteronomy 20:13

20:13 The Lord your God will deliver it over to you and you must kill every single male by the sword.

Deuteronomy 20:16-18

Laws Concerning War with Canaanite Nations

20:16 As for the cities of these peoples that the Lord your God is going to give you as an inheritance, you must not allow a single living thing to survive. 20:17 Instead you must utterly annihilate them – the Hittites, Amorites, Canaanites, Perizzites, Hivites, and Jebusites – just as the Lord your God has commanded you, 20:18 so that they cannot teach you all the abhorrent ways they worship their gods, causing you to sin against the Lord your God.