Deuteronomy 20:10-20

¹⁰"When you draw near to a city to fight against it, offer terms of peace to it. ¹¹And if its answer to you is peace and it opens to you, then all the people who are found in it shall do forced labor for you and shall serve you. ¹²But if it makes no peace with you, but makes war against you, then you shall besiege it; ¹³and when the LORD your God gives it into your hand you shall put all its males to the sword, ¹⁴but the women and the little ones, the cattle, and everything else in the city, all its spoil, you shall take as booty for yourselves; and you shall enjoy the spoil of your enemies, which the LORD your God has given you. ¹⁵Thus you shall do to all the cities which are very far from you, which are not cities of the nations here. ¹⁶But in 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 Hittites and the Amorites, the Canaanites and the Per'izzites, the Hivites and the Jeb'usites, as the LORD your God has commanded; ¹⁸that they may not teach you to do according to all their abominable practices which they have done in the service of their gods, and so to sin against the LORD your God.

¹⁹"When you besiege a city for a long time, making war against it in order to take it, you shall not destroy its trees by wielding an axe against them; for you may eat of them, but you shall not cut them down. Are the trees in the field men that they should be besieged by you? ²⁰Only the trees which you know are not trees for food you may destroy and cut down that you may build siegeworks against the city that makes war with you, until it falls.