For the affront and injury which they offered to God, partly by their own idolatry and lewdness, and partly by seducing God's people into rebellion against him. God's great care was to avenge the Israelites, Numbers 31:2, and Moses's chief desire was to avenge God rather than himself or the people. Withal he doth hereby insinuate, that God and his people have the same cause, the same friends and enemies.
Related Commentaries of Numbers 31:3
Numbers 31:3
3 And Moses spake unto the people, saying, Arm some of yourselves unto the war, and let them go against the Midianites, and avenge the LORD of Midian.