Numbers 19:18-19

18A person who is clean is to take hyssop, dip it in the water, and sprinkle the tent, all the furnishings, and the people who were there. He is also to sprinkle the one who touched a bone, a grave, a corpse, or a person who had been killed.

19“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.