Deuteronomy 20:10-15

When you march up to attack a city, first make them an offer of peace. If they accept your offer and open their gates to you, all the people of that city will become your slaves and work for you. But if they do not make peace with you and fight you in battle, you should surround that city. The LORD your God will give it to you. Then kill all the men with your swords, and you may take everything else in the city for yourselves. Take the women, children, and animals, and you may use these things the LORD your God gives you from your enemies. Do this to all the cities that are far away, that do not belong to the nations nearby.