Numbers 19:10-12

10And the one who gathers the ashes of the heifer shall wash his clothes, and be unclean until evening. It shall be a statute forever to the children of Israel and to the stranger who dwells among them.

11‘He who touches the dead body of anyone shall be unclean seven days.

12He shall purify himself with the water on the third day and on the seventh day; then he will be clean. But if he does not purify himself on the third day and on the seventh day, he will not be clean.