Numbers 19:9-10

9Now a man who is clean shall gather up the ashes of the heifer and deposit them outside the camp in a clean place, and 1the congregation of the sons of Israel shall keep it as 2water to remove impurity; it is 3purification from sin. 10The one who gathers the ashes of the heifer 4shall wash his clothes and be unclean until evening; and it shall be a perpetual statute to the sons of Israel and to the alien who sojourns among them.