Moses was angry with the officers of the army1--the commanders of thousands and commanders of hundreds--who returned from the battle.
References for Numbers 31:14
"Have you allowed all the women to live?" he asked them.
"They were the ones who followed Balaam's advice2 and were the means of turning the Israelites away from the LORD in what happened at Peor,3 so that a plague4 struck the LORD's people.
References for Numbers 31:16