Deuteronomy 20:11-13

Amplified Bible

¹¹ If that city accepts your terms of peace and opens its gates to you, then all the people who are found in it shall become your forced labor and shall serve you. ¹² However, if it does not make peace with you, but makes war against you, then you shall lay siege to it. ¹³ When the Lord your God gives it into your hand, you shall strike down all the men in it with the edge of the sword.