Numbers 19:7-8, 19

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

Then the clean person shall sprinkle [the water for purification] on the unclean person on the third day and on the seventh day, and on the seventh day the unclean man shall purify himself, and wash his clothes and bathe himself in water, and shall be [ceremonially] clean at evening.