Num 31:21-24

21Eleazar the priest said to the troops who had gone to battle: “This is the statute of the law that the Lord has commanded Moses:22gold, silver, bronze, iron, tin, and lead—23everything that can withstand fire, shall be passed through fire, and it shall be clean. Nevertheless it shall also be purified with the water for purification; and whatever cannot withstand fire, shall be passed through the water.24You must wash your clothes on the seventh day, and you shall be clean; afterward you may come into the camp.”