Joshua 8:1; Joshua 8:3

1 Then the LORD said to Joshua, “Do not be afraid; do not be discouraged. Take the whole army with you, and go up and attack Ai. For I have delivered into your hands the king of Ai, his people, his city and his land.

3 So Joshua and the whole army moved out to attack Ai. He chose thirty thousand of his best fighting men and sent them out at night