Joshua 8:1-3

And Jehovah said unto Joshua, Fear not, neither be thou dismayed: take all the people of war with thee, and arise, go up to Ai; see, I have given into thy hand the king of Ai, and his people, and his city, and his land; 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. 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.