Numbers 31:15-18

15“Have you spared all the women?” he asked them. 16“Look, these women caused the sons of Israel, through the counsel of Balaam, to turn unfaithfully against the LORD at Peor, so that the plague struck the congregation of the LORD. 17So now, kill all the boys, as well as every woman who has had relations with a man, 18but spare for yourselves every girl who has never had relations with a man.