Numbers 31:17-19

New Revised Standard Version, Anglicised

¹⁷ Now therefore, kill every male among the little ones, and kill every woman who has known a man by sleeping with him. ¹⁸ But all the young girls who have not known a man by sleeping with him, keep alive for yourselves. ¹⁹ Camp outside the camp for seven days; whoever of you has killed any person or touched a corpse, purify yourselves and your captives on the third and on the seventh day.