Numbers 19:7-8, 19

Then the priest shall wash his clothes, he shall bathe in water, and afterward he shall come into the camp; the priest shall be unclean until evening. And the one who burns it shall wash his clothes in water, bathe in water, and shall be unclean until evening.

The clean person shall sprinkle the unclean on the third day and on the seventh day; and on the seventh day he shall purify himself, wash his clothes, and bathe in water; and at evening he shall be clean.