Numbers 19:17-19

And for an unclean {person} they shall take of the ashes of the burnt heifer of purification for sin, and running water shall be put thereto in a vessel: {ashes: Heb. dust} {running...: Heb. living waters shall be given} And a clean person shall take hyssop, and dip {it} in the water, and sprinkle {it} upon the tent, and upon all the vessels, and upon the persons that were there, and upon him that touched a bone, or one slain, or one dead, or a grave: And the clean {person} shall sprinkle upon the unclean on the third day, and on the seventh day: and on the seventh day he shall purify himself, and wash his clothes, and bathe himself in water, and shall be clean at even.