Joshua 8:1-3

Now the LORD said to Joshua, “Do not fear or be dismayed (intimidated). Take all the men of war with you and set out, go up to Ai; see, I have given the king of Ai, his people, his city, and his land into your hand. You shall do [the same] to Ai and its king as you did to Jericho and its king; [except that] you shall take only its spoil and its cattle as plunder for yourselves. Set up an ambush for the city behind it [on the west side].” So Joshua set out with all the people of war to go up against Ai; then Joshua chose thirty thousand valiant men, and sent them out at night.