Numbers 31:17-19

Amplified Bible

¹⁷ Now therefore, kill every male among the children, and kill every woman who is not a virgin. ¹⁸ But all the young girls who have not known a man intimately, keep alive for yourselves [to marry]. ¹⁹ Camp outside the camp for seven days; whoever has killed any person and whoever has touched any dead body, purify yourselves and your captives, on the third day and on the seventh day.