Numbers 31:19-24

19“You are to remain outside the camp for seven days. All of you and your prisoners who have killed a person or touched the dead are to purify yourselves on the third day and the seventh day.

20Also purify everything: garments, leather goods, things made of goat hair, and every article of wood.”

21Then the priest Eleazar said to the soldiers who had gone to battle, “This is the legal statute the Lord commanded Moses:

22The gold, silver, bronze, iron, tin, and lead —

23everything that can withstand fire — you are to pass through fire, and it will be clean. It must still be purified with the purification water. Anything that cannot withstand fire, pass through the water.

24On the seventh day wash your clothes, and you will be clean. After that you may enter the camp.”