Numbers 19
19 Ref Let the clean person do this to the unclean on the third day and on the seventh day: and on the seventh day he is to make him clean; and after washing his clothing and bathing himself in water, he will be clean in the evening.
20 Ref But the man who, being unclean, does not make himself clean in this way, will be cut off from the meeting of the people, because he has made the holy place of the Lord unclean: the water has not been put on him, he is unclean.
21 Ref This is to be a law for them for ever: he who puts the water on the unclean person is to have his clothing washed; and anyone touching the water will be unclean till evening.