Numbers 19:18 (BSB)

Then a man who is ceremonially clean is to take some 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, or a person who has died or been slain.

From Numbers 19. Also in the ESV.

Commentary on Numbers 19:18

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Numbers 19:11-22: Directions are here given concerning the use and application of the ashes which were prepared for purification. they were laid up to be laid out; and therefore, though now one place would serve to keep them in, while all Israel lay so closely encamped, yet it is probable that afterwards, when they came to Canaan, some of these ashes were kept in every town, for...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Numbers 19:18: And a clean person shall take hyssop, and dip it in the water,.... Three stalks of hyssop bound together, as the Targum of Jonathan, and this man was to be a clean priest, according to the same; but it does not seem necessary that he should be a priest, but that anyone free from ceremonial pollution might do it: and sprinkle it upon the tent...
• Geneva Bible Notes (Reformed), Geneva Bible Study Notes on Numbers 19:18: And a clean person shall take hyssop, and dip [it] in the water, and sprinkle [it] upon the tent, and upon all the vessels, and upon the persons that were there, and upon him that touched a bone, or one slain, or one dead, or a grave: (k) One of the priests who is clean.
• Keil & Delitzsch (Lutheran), Biblical Commentary on the Old Testament on Numbers 19:17-20: Num 19:17-20 Ceremony of purification. They were to take for the unclean person some of the dust of the burning of the cow, i.e., some of the ashes obtained by burning the cow, and put living, i.e., fresh water (see Lev 14:5), upon it in a vessel.