Numbers 19:18-19

18And a clean person shall take hyssop and dip it in the water, and sprinkle it on the tent, on all the furnishings, on the persons who were there, and on the one who touched the bone or the one who was killed or the one who died naturally, or the grave. 19Then the clean person 1shall sprinkle on the unclean on the third day and on the seventh day; and on the seventh day he shall purify him, and he shall wash his clothes and bathe himself in water and will be clean by evening.