Numbers 19:6, 18

The priest shall take cedar wood and hyssop and scarlet [material] and cast them into the midst of the burning heifer.

A clean person shall take hyssop and dip it in the water and sprinkle it on the tent and on all the furnishings and on the people who were there, and on the one who touched the bone or the one who was killed or the one who died [naturally] or the grave.