Numbers 31:14 (KJV)

And the children of Israel took all the women of Midian captives, and their little ones, and took the spoil of all their cattle, and all their flocks, and all their goods.

And they burnt all their cities wherein they dwelt, and all their goodly castles, with fire.

And they took all the spoil, and all the prey, both of men and of beasts.

And they brought the captives, and the prey, and the spoil, unto Moses, and Eleazar the priest, and unto the congregation of the children of Israel, unto the camp at the plains of Moab, which are by Jordan near Jericho.

And Moses, and Eleazar the priest, and all the princes of the congregation, went forth to meet them without the camp.

And Moses said unto them, Have ye saved all the women alive?

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.

Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.

But all the women children, that have not known a man by lying with him, keep alive for yourselves.

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.