Numbers 31:18 in the World English Bible
But all the girls, who have not known man by lying with him, keep alive for yourselves.
Context
17 Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.
18 But all the women children, that have not known a man by lying with him, keep alive for yourselves.
19 And do ye abide without the camp seven days: whosoever hath killed any person, and whosoever hath touched any slain, purify both yourselves and your captives on the third day, and on the seventh day.