Holy bible

Deuteronomy 20

Laws for Going to War

10-15 Before you attack a town that is far from your land, offer peace to the people who live there. If they surrender and open their town gates, they will become your slaves. But if they reject your offer of peace and try to fight, surround their town and attack. Then, after the Lord helps you capture it, kill all the men. Take the women and children as slaves and keep the livestock and everything else of value.

16 Whenever you capture towns in the land the Lord your God is giving you, be sure to kill all the people and animals.
17 He has commanded you to completely wipe out the Hittites, the Amorites, the Canaanites, the Perizzites, the Hivites, and the Jebusites.
18 If you allow them to live, they will persuade you to worship their disgusting gods, and you will be unfaithful to the Lord.