Deuteronomy 20:15-19

¹⁵So shalt thou do to all cities that are at a great distance from thee, and are not of these cities which thou shalt receive in possession.

¹⁶But of those cities that shall be given thee, thou shalt suffer none at all to live:

¹⁷But shalt kill them with the edge of the sword, to wit, the Hethite, and the Amorrhite, and the Chanaanite, the Pherezite, and the Hevite, and the Jebusite, as the Lord thy God hath commanded thee:

¹⁸Lest they teach you to do all the abominations which they have done to their gods: and you should sin against the Lord your God.

¹⁹When thou hast besieged a city a long time, and hath compassed it with bulwarks to take it, thou shalt not cut down the trees that may be eaten of, neither shalt thou spoil the country round about with axes: for it is a tree, and not a man, neither can it increase the number of them that fight against thee.