Numbers 31:21-23

21Then Eleazar the priest said to the men of war who had gone to battle, “This is the statute of the law which the Lord has commanded Moses:

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.