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.”
And one shall burn the heifer in his sight; her skin, and her flesh, and her blood, with her dung, shall he burn:
And the priest shall take cedar wood, and hyssop, and scarlet, and cast it into the midst of the burning of the heifer.
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.
And he that burneth her shall wash his clothes in water, and bathe his flesh in water, and shall be unclean until the even.
And a man that is clean shall gather up the ashes of the heifer, and lay them up without the camp in a clean place, and it shall be kept for the congregation of the children of Israel for a water of separation: it is a purification for sin.
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Cross-References
“And he that eateth of the carcase of it shall wash his clothes, and be unclean until the even: he also that beareth the carcase of it shall wash his clothes, and be unclean until the even.”
“Moreover he that goeth into the house all the while that it is shut up shall be unclean until the even.”
“And he that let go the goat for the scapegoat shall wash his clothes, and bathe his flesh in water, and afterward come into the camp.”
“The soul which hath touched any such shall be unclean until even, and shall not eat of the holy things, unless he wash his flesh with water.”
“And thus shalt thou do unto them, to cleanse them: Sprinkle water of purifying upon them, and let them shave all their flesh, and let them wash their clothes, and so make themselves clean.”