Numbers 19:10-12

10Then the one who gathers up the cow’s ashes must wash his clothes, and he will remain unclean until evening. This is a permanent statute for the Israelites and for the alien who resides among them.

11“The person who touches any human corpse will be unclean for seven days.

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