Numbers 19:5-7

⁵Then, while Eleazar watches, the cow must be burned completely—its hide, its meat, the rest of its blood, and even its dung.

⁶Eliezer then must take a stick of cedar wood, a stalk of a plant named hyssop, and some scarlet/red yarn, and throw them into the fire where the cow is burning.

⁷Then the priest must wash his clothes and bathe. After doing that, he may return to the camp. But he will be unfit for doing any sacred work until that evening.