Charles Ellicott Commentary Numbers 19:7

"Then the priest shall wash his clothes, and he shall bathe his flesh in water, and afterward he shall come into the camp, and the priest shall be unclean until the even." — Numbers 19:7 (ASV)

Then the priest ... — The Targum of Jonathan refers these words to the priest who killed the heifer, and Ibn Ezra to the priest who burnt it; but the reference is more probably, as in the preceding verse, to Eleazar.