Numbers 31:1-6

1And the LORD spoke to Moses, saying, 2Avenge the children of Israel of the Midianites: afterward shalt thou be gathered to thy people. 3And Moses spoke to the people, saying, Arm some of yourselves for the war, and let them go against the Midianites, and avenge the LORD on Midian. 4Of every tribe a thousand, throughout all the tribes of Israel, shall ye send to the war.1 5So there were delivered out of the thousands of Israel, a thousand of every tribe, twelve thousand armed for war. 6And Moses sent them to the war, a thousand of every tribe, them and Phinehas the son of Eleazar the priest, to the war, with the holy instruments, and the trumpets to blow in his hand.