Deuteronomy 13:15-17

you shall surely strike the inhabitants of that city with the edge of the sword, utterly destroying it and all that is in it and its cattle with the edge of the sword. Then you shall gather all its booty into the middle of its open square and burn the city and all its booty with fire as a whole burnt offering to the LORD your God; and it shall be a ruin forever. It shall never be rebuilt. Nothing from that which is put under the ban shall cling to your hand, in order that the LORD may turn from His burning anger and show mercy to you, and have compassion on you and make you increase, just as He has sworn to your fathers