Deuteronomy 20:12-16

However, if it does not make peace with you, but makes war against you, then you shall besiege it.

When the Lord your God gives it into your hand, you shall strike all the men in it with the edge of the sword.

However, the women, the children, the animals, and everything that is in the city, all of its spoils, you shall take as plunder for yourself; and you shall use the spoils of your enemies which the Lord your God has given you.

This is what you shall do to all the cities that are very far from you, which are not of the cities of these nations nearby.

Only in the cities of these peoples that the Lord your God is giving you as an inheritance, you shall not leave anything that breathes alive.