Deuteronomy 20:15-18

15This is how you are to treat all the cities that are far away from you and are not among the cities of these nations.

16However, you must not let any living thing survive among the cities of these people the Lord your God is giving you as an inheritance.

17You must completely destroy them — the Hethite, Amorite, Canaanite, Perizzite, Hivite, and Jebusite — as the Lord your God has commanded you,

18so that they won’t teach you to do all the detestable acts they do for their gods, and you sin against the Lord your God.