Numbers 19:6

19:6 And the priest must take cedar wood, hyssop, and scarlet wool and throw them into the midst of the fire where the heifer is burning.

Numbers 19:18

19:18 Then a ceremonially clean person must take hyssop, dip it in the water, and sprinkle it on the tent, on all its furnishings, and on the people who were there, or on the one who touched a bone, or one killed, or one who died, or a grave.