Numbers 19:19-20

19And the clean person must splash the water on the unclean person on the third day too. And he must do it on the seventh day. On the seventh day he will make the person clean again. Then the person who had not been clean must wash his clothes. And he must wash himself in water. In the evening, that person will become clean.

20The person who is not clean might not wash himself and his clothes. If he does not do it, you must make that person separate from the people. That is because he has made the Lord's Holy Place become unclean. Because the priest did not splash special water on him he will not be clean.