Deuteronomy 20:10-15

10When thou drawest nigh unto a city to fight against it, then proclaim peace unto it. 11And it shall be, if it make thee answer of peace, and open unto thee, then it shall be, that all the people that are found therein shall become tributary unto thee, and shall serve thee. 12And if it will make no peace with thee, but will make war against thee, then thou shalt besiege it: 13and when Jehovah thy God delivereth it into thy hand, thou shalt smite every male thereof with the edge of the sword: 14but the women, and the little ones, and the cattle, and all that is in the city, even all the spoil thereof, shalt thou take for a prey unto thyself; and thou shalt eat the spoil of thine enemies, which Jehovah thy God hath given thee. 15Thus shalt thou do unto all the cities which are very far off from thee, which are not of the cities of these nations.