Numbers 19:17-19

17‘And for an unclean person they shall take some of the ashes of the heifer burnt for purification from sin, and running water shall be put on them in a vessel.

18A clean person shall take hyssop and dip it in the water, sprinkle it on the tent, on all the vessels, on the persons who were there, or on the one who touched a bone, the slain, the dead, or a grave.

19The 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.