Deuteronomy 20:11-15

If they accept your terms and open the gates to you, then all the people inside will serve you in forced labor. But if they refuse to make peace and prepare to fight, you must attack the town. When the LORD your God hands the town over to you, use your swords to kill every man in the town. But you may keep for yourselves all the women, children, livestock, and other plunder. You may enjoy the plunder from your enemies that the LORD your God has given you. “But these instructions apply only to distant towns, not to the towns of the nations in the land you will enter.