Numbers 31:22-24

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