Numbers 19:7-10

7Then the priest shall wash his clothes and bathe his body in water; and afterward come into the camp, but he shall be [ceremonially] unclean until evening.

8The one who burns the heifer shall wash his clothes and bathe his body in water, and shall be unclean until evening.

9Now a man who is [ceremonially] clean shall collect the ashes of the heifer and deposit them outside the camp in a clean place, and the congregation of the Israelites shall keep it for water to remove impurity; it is [to be used for] purification from sin.

10The one who gathers the ashes of the heifer shall wash his clothes, and be unclean until evening. This shall be a perpetual statute to the Israelites and to the stranger who lives as a resident alien among them.