Numbers 19:16-18, 20-21

If anyone is outside and touches someone who was killed by a sword or who died a natural death, or if anyone touches a human bone or a grave, that person will be unclean for seven days. “So you must use the ashes from the burnt offering to make that person clean again. Pour fresh water over the ashes into a jar. A clean person must take a hyssop branch and dip it into the water, and then he must sprinkle it over the tent and all its objects. He must also sprinkle the people who were there, as well as anyone who touched a bone, or the body of someone who was killed, or a dead person, or a grave.

If any who are unclean do not become clean, they must be cut off from the community. Since they were not sprinkled with the cleansing water, they stay unclean, and they could make the LORD’s Holy Tent unclean. This is a lasting rule. Those who sprinkle the cleansing water must also wash their clothes, and anyone who touches the water will be unclean until evening.