Numbers 31:10-20

10 And they burnt all their cities in which they dwelt, and all their goodly castles, with fire.
11 And they took all the spoil, and all the prey, [both] of men and of beasts.
12 And they brought the captives, and the prey, and the spoil to Moses and Eleazar the priest, and to the congregation of the children of Israel, to the camp at the plains of Moab, which [are] by Jordan [near] Jericho.
13 And Moses, and Eleazar the priest, and all the princes of the congregation, went forth to meet them without the camp.
14 And Moses was wroth with the officers of the host, [with] the captains over thousands, and captains over hundreds, who came from the battle.
15 And Moses said to them, Have ye saved all the women alive?
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.
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 female 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: whoever hath killed any person, and whoever hath touched any slain, purify [both] yourselves and your captives on the third day, and on the seventh day.
20 And purify all [your] raiment, and all that is made of skins, and all work of goats' [hair], and all things made of wood.