Numbers 31:5

Overview - Numbers 31
1	The Midianites are spoiled, and Balaam slain.
13	Moses is wroth with the officers, for saving the women alive.
19	How the soldiers, with their captives and spoil, are to be purified.
25	The proportion in which the prey is to be divided.
48	The voluntary oblation unto the treasury of the Lord.

Numbers 31:5  (King James Version)
So there were delivered out of the thousands of Israel, a thousand of every tribe, twelve thousand armed for war.