Numbers 31:22-24

22Only the gold, silver, bronze, iron, tin, and lead— 23everything that can withstand the fire—must be put through the fire, and it will be clean. But it must still be purified with the water of purification. And everything that cannot withstand the fire must pass through the water. 24On the seventh day you are to wash your clothes, and you will be clean. After that you may enter the camp.”