The man who has gathered up the ashes of the heifer must also wash his clothes, and he will be ceremonially unclean until evening. This is a permanent statute for the Israelites and for the foreigner residing among them.
We have here the divine appointment concerning the solemn burning of a red heifer to ashes, and the preserving of the ashes, that of them might be made, not a beautifying, but a purifying, water, for that was the utmost the law reached to; it offered not to adorn as the gospel does, but to cleanse only.
Commenting on Numbers 19:1-10
And he that gathereth the ashes of the heifer shall wash his clothes,.... Whom the Targum of Jonathan calls a priest, though it does not seem necessary he should be one: and be unclean until the even; See Gill on Num 19:7, and it shall be unto the children of Israel, and unto the stranger that sojourneth among them, for a statute for ever; until...
Num 19:2-10 Preparation of the Purifying Water. - As water is the ordinary means by which all kinds of uncleanness are removed, it was also to be employed in the removal of the uncleanness of death. But as this uncleanness was the strongest of all religious defilements, fresh water alone was not sufficient to remove it; and consequently a certain kind of sprinkling-water was appointed...
Commenting on Numbers 19:2-10