Deuteronomy 13:15-18

15you must attack that town and completely destroy all its inhabitants, as well as all the livestock.

16Then you must pile all the plunder in the middle of the open square and burn it. Burn the entire town as a burnt offering to the Lord your God. That town must remain a ruin forever; it may never be rebuilt.

17Keep none of the plunder that has been set apart for destruction. Then the Lord will turn from his fierce anger and be merciful to you. He will have compassion on you and make you a large nation, just as he swore to your ancestors.

18“The Lord your God will be merciful only if you listen to his voice and keep all his commands that I am giving you today, doing what pleases him.