Numbers 31:2-6

ISV(i) 2 “Be sure to exact vengeance on behalf of the Israelis from the Midianites, after which you’ll be taken home to your people.”
3 So Moses instructed the people, “Muster your men of war to attack the Midianites and deliver the LORD’S vengeance against Midian. 4 Send 1,000 men to war from every tribe throughout all of Israel.” 5 So 1,000 men from every tribe—12,000 from the thousands of Israel—were mustered and equipped for war.
6 Moses sent 1,000 men from every tribe to fight against them, along with Eleazar’s son Phinehas, in whose hands were the articles of the sanctuary and trumpets to sound battle alarms.