Joshua 8
2 Ref And thou shalt do to Ai and her king as thou didst unto Jericho and her king: only the spoil thereof, and the cattle thereof, shall ye take for a prey unto yourselves: set thee an ambush for the city behind it.
3 Ref So Joshua arose, and all the people of war, to go up to Ai: and Joshua chose out thirty thousand men, the mighty men of valor, and sent them forth by night.