Numbers 31:14-18

But Moses was furious with all the generals and captains who had returned from the battle. “Why have you let all the women live?” he demanded. “These are the very ones who followed Balaam’s advice and caused the people of Israel to rebel against the LORD at Mount Peor. They are the ones who caused the plague to strike the LORD’s people. So kill all the boys and all the women who have had intercourse with a man. Only the young girls who are virgins may live; you may keep them for yourselves.