Numbers 31:22-24

22Only the gold, and the silver, the copper, the iron, the tin, and the lead,

23everything that passeth through the fire, ye shall make it go through the fire, and it shall be clean; only it shall be purified with the water of separation; and everything that cannot pass through the fire ye shall make go through the water.

24And ye shall wash your garments on the seventh day, and ye shall be clean; and afterwards ye may come into the camp.