Numbers 31:19-24

191And as for you, camp outside the camp for seven days; whoever has killed a person and whoever has touched anyone killed, purify yourselves, you and your captives, on the third day and on the seventh day. 20And you shall purify for yourselves every garment, every article of leather, every work of goats’ hair, and every article of wood.”

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 2withstand the fire, you shall pass through the fire, and it will be clean, only it shall be purified with 3water for impurity. But whatever cannot 4withstand the fire you shall pass through the water. 24And you shall wash your clothes on the seventh day and you will be clean; and afterward you may enter the camp.”