Numbers 31:21-23

21Then Eleazar the priest said to the men of war who had gone into the battle, “This is the ordinance of the law that the Lord commanded Moses:

22‘Only the gold, the silver, the bronze, the iron, the tin, and the lead,

23everything that may stand the fire, you are to pass through the fire, and it will be ceremonially clean, but it must still be purified with the water of purification. Anything that cannot withstand the fire you must pass through the water.