Numbers 19:19-20
19:19 And the clean person must sprinkle the unclean on the third day and on the seventh day; and on the seventh day he must purify him, and then he must wash his clothes, and bathe in water, and he will be clean in the evening.
19:20 But the man who is unclean and does not purify himself, that person must be cut off from among the community, because he has polluted the sanctuary of the Lord; the water of purification was not sprinkled on him, so he is unclean.