Numbers 19:8, 19

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.