Deuteronomy 20:15-19

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

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

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

¹⁸that they not teach you to follow all their abominations, which they have done for their gods; so would you sin against the LORD your God.

¹⁹When you shall besiege a city a long time, in making war against it to take it, you shall not destroy its trees by wielding an axe against them; for you may eat of them. You shall not cut them down, for is the tree of the field man, that it should be besieged by you?