(31:15) And Moses said unto them, Have ye saved all the women alive?  
(31:16) Behold, these caused the children of Israel, through the counsel of
Balaam, to commit trespass against the LORD in the matter of Peor, and there
was a plague among the congregation of the LORD.  
(31:17) Now therefore kill every male among the little ones, and kill every
woman that hath known man by lying with him.
(31:18) But all the women children, that have not known a man by lying with
him, keep alive for yourselves.  

++ The Bible, Book of Numbers