Numbers 19:16-18

161Also, anyone who in the open field touches one who has been killed with a sword or one who has died naturally, or touches a human bone or a grave, will be unclean for seven days.

17Then for the unclean person they shall take some of the 2ashes of the 3burnt 45purification from sin and 6running water shall be 7added to them in a container.

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.