Deuteronômio 20

10 When you come to a town, before attacking it, make an offer of peace.

11 And if it gives you back an answer of peace, opening its doors to you, then all the people in it may be put to forced work as your servants.

12 If however it will not make peace with you, but war, then let it be shut in on all sides:

13 And when the Lord your God has given it into your hands, let every male in it be put to death without mercy.