Numbers 31:22-24

22The gold, silver, bronze, iron, tin, lead,

23and anything able to pass through fire is to be put through the fire and will then be clean. It is also to be purified with the water of cleansing. Anything that cannot stand the fire is to be put through the water.

24You are to wash your clothes also on the seventh day. You will then be clean and may then come into the camp.”