Numbers 31:2-6

2“Take vengeance on the Midianites for the Israelites. After that, you will be gathered to your people.” 3So Moses said to the people, “Arm some of your men to go to war against the Midianites so that they may carry out the Lord’s vengeance on them. 4Send into battle a thousand men from each of the tribes of Israel.” 5So twelve thousand men armed for battle, a thousand from each tribe, were supplied from the clans of Israel. 6Moses sent them into battle, a thousand from each tribe, along with Phinehas son of Eleazar, the priest, who took with him articles from the sanctuary and the trumpets for signaling.