Gather all the possessions of the people who lived there, and pile them up in the marketplace, without keeping anything for yourself. Set the pile and the whole town on fire, and don't ever rebuild the town. The whole town will be a sacrifice to the LORD your God. Then he won't be angry anymore, and he will have mercy on you and make you successful, just as he promised your ancestors.
Joshua made sure every building in Ai was burned to the ground. He told his men to kill the king of Ai and hang his body on a tree. Then at sunset he told the Israelites to take down the body, throw it in the gateway of the town, and cover it with a big pile of rocks. Those rocks are still there, and the town itself has never been rebuilt.