Joshua 8:1-2

Then the Lord said to Joshua, Have no fear and do not be troubled: take with you all the fighting-men and go up against Ai: for I have given into your hands the king of Ai and his people and his town and his land: And you are to do to Ai and its king as you did to Jericho and its king: but their goods and their cattle you may take for yourselves: let a secret force be stationed to make a surprise attack on the town from the back.