Deuteronomy 20:10-15

10When thou approachest unto a city to fight against it, thou shalt proclaim peace unto it.

11And it shall be, if it make thee answer of peace, and open unto thee, then all the people that are found therein shall be tributaries unto thee, and they shall serve thee.

12And if it will not make peace with thee, but will make war with thee, then thou shalt besiege it;

13and when Jehovah thy 1God delivereth it into thy hand, thou shalt smite every male thereof with the edge of the sword:

14only the women, and the little ones, and the cattle, and all that shall be in the city, all the spoil thereof, shalt thou take as booty for thyself; and thou shalt eat the spoil of thine enemies, which Jehovah thy 2God giveth thee

15Thus shalt thou do unto all the cities that are very far off from thee, which are not of the cities of these nations.