Numbers 19:19-20

The person who is clean must sprinkle this water on the unclean people on the third day and on the seventh day. On the seventh day they will become clean. They must wash their clothes and take a bath, and they will be clean that evening. 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.