Numbers 31:15-20

And Moses said to them: “Have you kept all the women alive? Look, these women caused the children of Israel, through the counsel of Balaam, to trespass against the LORD in the incident of Peor, and there was a plague among the congregation of the LORD. Now therefore, kill every male among the little ones, and kill every woman who has known a man intimately. But keep alive for yourselves all the young girls who have not known a man intimately. And as for you, remain outside the camp seven days; whoever has killed any person, and whoever has touched any slain, purify yourselves and your captives on the third day and on the seventh day. Purify every garment, everything made of leather, everything woven of goats’ hair, and everything made of wood.”