Numbers 19:10-20

10 The person who collected the ashes from the cow must also wash his clothes. He will be unclean until evening. This will be a permanent law for the Israelites and for the foreigners who live with them.
11 "Whoever touches the dead body of any human being will be unclean for seven days.
12 The unclean person must use this water on the third day and the seventh day to take away his sin. Then he will be clean. But if he doesn't use this water on the third day and the seventh day, he will not be clean.
13 Whoever touches the dead body of a human being and doesn't use this water to take away his sin makes the LORD's tent unclean. That person must be excluded from Israel, because the water that takes away uncleanness wasn't sprinkled on him. He is unclean; his uncleanness stays with him.
14 "These are your instructions for when a person dies in a tent: Everyone who goes into the tent and everyone who is in the tent will be unclean for seven days.
15 Every container without a lid fastened on it is unclean.
16 "Whoever is outdoors and touches someone who was killed or has died naturally or anyone who touches a human bone or a grave will be unclean for seven days.
17 "[This is what you must do] for people who become unclean from touching a dead body. Put some of the ashes from the red cow that was burned as an offering for sin into a container. Then pour fresh water on them.
18 A person who is clean will take a sprig of hyssop, dip it in the water, and sprinkle the tent, all the furnishings, and all the people who were in the tent [with the dead body]. He must also sprinkle any person who has touched a human bone or a grave and any person who has touched someone who has been killed or who has died naturally.
19 A person who is clean will sprinkle these types of unclean people on the third day and the seventh day. On the seventh day the clean person will finish taking away their sins. Then they must wash their clothes and bodies, and in the evening they will be clean.
20 But if the person who becomes unclean doesn't have his sin taken away, that person must be excluded from the assembly. He has made the holy place of the LORD unclean. The water to take away uncleanness wasn't sprinkled on him. He is unclean.