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, the silver, the bronze, the iron, the tin, and the lead,

23everything that can stand fire, you shall pass through fire, and it shall be clean. Nevertheless, it shall also be purified with the water of purification [to remove its impurity]; and all that cannot stand fire [such as fabrics] you shall pass through water.