Numbers 19:10-12

10The person who collected the ashes from the cow must also wash his clothes. He will be unclean until evening. This will be a permanent law for the Israelites and for the foreigners who live with them.

11“Whoever touches the dead body of any human being will be unclean for seven days.

12The unclean person must use this water on the third day and the seventh day to take away his sin. Then he will be clean. But if he doesn’t use this water on the third day and the seventh day, he will not be clean.