Deuteronomy 20:15-19

¹⁵You must act in this way toward all the cities that are very far from you, cities that are not of the cities of these following nations.

¹⁶In the cities of these peoples that Yahweh your God is giving you as an inheritance, you must save alive nothing that breathes.

¹⁷Instead, you must completely destroy them: the Hittite, and the Amorite, the Canaanite, the Perizzite, the Hivite, and the Jebusite, as Yahweh your God has commanded you.

¹⁸Do this so that they do not teach you to act in any of their abominable ways, as they have done with their gods. If you do, you will sin against Yahweh your God.

¹⁹When you will besiege a city for a long time, as you wage war against it to capture it, you must not destroy its trees by wielding an ax against them. For you may eat from them, so you must not cut them down. For is the tree of the field a man whom you should besiege?