Numbers 31:22-24

22only the gold and the silver, the bronze, the iron, the tin, and the lead, 23everything that can 1withstand the fire, you shall pass through the fire, and it will be clean, only it shall be purified with 2water for impurity. But whatever cannot 3withstand the fire you shall pass through the water. 24And you shall wash your clothes on the seventh day and you will be clean; and afterward you may enter the camp.”