Numbers 19:9, 18

Then someone who is ceremonially clean will gather up the ashes of the heifer and deposit them in a purified place outside the camp. They will be kept there for the community of Israel to use in the water for the purification ceremony. This ceremony is performed for the removal of sin.

Then someone who is ceremonially clean must take a hyssop branch and dip it into the water. That person must sprinkle the water on the tent, on all the furnishings in the tent, and on the people who were in the tent; also on the person who touched a human bone, or touched someone who was killed or who died naturally, or touched a grave.