Joshua 8:3
8:3 Joshua and the whole army marched against Ai. Joshua selected thirty thousand brave warriors and sent them out at night.
Joshua 8:24-25
8:24 When Israel had finished killing all the men of Ai who had chased them toward the desert (they all fell by the sword), all Israel returned to Ai and put the sword to it.
8:25 Twelve thousand men and women died that day, including all the men of Ai.