Numbers 19:7-8, 19

Then the priest must wash his clothes and bathe his body in water; after that he may enter the camp, but he will remain ceremonially unclean until evening. The one who burned the cow must also wash his clothes and bathe his body in water, and he will remain unclean until evening.

“The one who is clean is to sprinkle the unclean person on the third day and the seventh day. After he purifies the unclean person on the seventh day, the one being purified must wash his clothes and bathe in water, and he will be clean by evening.