Numbers 19:5-9

Then the heifer shall be burned in his sight; its hide, its flesh, and its blood, with its refuse, shall be burned.

And the priest shall take cedar wood, hyssop, and scarlet material, and throw it into the midst of the burning heifer.

The priest shall then wash his clothes and bathe his body in water, and afterward come into the camp; but the priest will be unclean until evening.

The one who burns the heifer shall also wash his clothes in water and bathe his body in water, and will be unclean until evening.

Now a man who is clean shall gather up the ashes of the heifer and put them outside the camp in a clean place, and the congregation of the sons of Israel shall keep them for water to remove impurity; it is purification from sin.