Numbers 19:5-7

⁵And the cow is to be burned before him, her skin and her flesh and her blood and her waste are to be burned:

⁶Then let the priest take cedar-wood and hyssop and red thread, and put them into the fire where the cow is burning.

⁷And the priest, after washing his clothing and bathing his body in water, may come back to the tent-circle, and will be unclean till evening.