Deuteronomy 20:10-20

10“When you approach a city to fight against it, you shall 1offer it terms of peace. 11If it 2agrees to make peace with you and opens to you, then all the people who are found in it shall become your 3forced labor and shall serve you. 12However, if it does not make peace with you, but makes war against you, then you shall besiege it. 13When the Lord your God gives it into your hand, 4you shall strike all the 5men in it with the edge of the sword. 14Only the women and the children and 6the animals and all that is in the city, all its spoil, you shall take as booty for yourself; and you shall 7use the spoil of your enemies which the Lord your God has given you. 15Thus you shall do to all the cities that are very far from you, which are not of the cities of these nations 8nearby. 169Only in the cities of these peoples that the Lord your God is giving you as an inheritance, you shall not leave alive anything that breathes. 17But you shall 10utterly destroy them, the Hittite and the Amorite, the Canaanite and the Perizzite, the Hivite and the Jebusite, as the Lord your God has commanded you, 18so that they may not teach you to do 11according to all their detestable things which they have done for their gods, so that you would 12sin against the Lord your God.

19“When you besiege a city a long time, to make war against it in order to capture it, you shall not destroy its trees by swinging an axe against them; for you may eat from them, and you shall not cut them down. 13For is the tree of the field a man, that it should 14be besieged by you? 20Only the trees which you know 15are not fruit trees you shall destroy and cut down, that you may construct siegeworks against the city that is making war with you until it falls.