Numbers 31:4

You must send to the battle a thousand men from every tribe throughout all the tribes of Israel.” ¹ 

Le 26:8; Jud 7:2; 1Sa 14:6

¹ sn Some commentators argue that given the size of the nation (which they reject) the small number for the army is a sign of the unrealistic character of the story. The number is a round number, but it is also a holy war, and God would give them the victory. They are beginning to learn here, and at Jericho, and later against these Midianites under Gideon, that God does not want or need a large army in order to obtain victory.