Numbers 19:16-20
16 “Anyone out in the open who touches someone who has been killed with a sword or someone who has died a natural death, or anyone who touches a human bone or a grave, will be unclean for seven days.
17 “For the unclean person, put some ashes from the burned purification offering into a jar and pour fresh water over them.
18 Then a man who is ceremonially clean is to take some hyssop, dip it in the water and sprinkle the tent and all the furnishings and the people who were there. He must also sprinkle anyone who has touched a human bone or a grave or someone who has been killed or someone who has died a natural death.
19 The man who is clean is to sprinkle the unclean person on the third and seventh days, and on the seventh day he is to purify him. The person being cleansed must wash his clothes and bathe with water, and that evening he will be clean.
20 But if a person who is unclean does not purify himself, he must be cut off from the community, because he has defiled the sanctuary of the Lord. The water of cleansing has not been sprinkled on him, and he is unclean.