Numbers 19:3

The work would necessarily require a priest; yet as it rendered him unclean for the day Numbers 19:22, the high priest was relieved from performing it.

Without the camp - The defilement was viewed as transferred to the victim that was to be offered for its removal. Under these circumstances the victim, like the defiled persons themselves, would be removed outside the camp. The particular pollution to be remedied by this ordinance was the indirect one resulting from contact with tokens and manifestations of sin, not the direct and personal one arising from actual commission of sin. So too the sinless antitype had to bear the reproach of associating with sinners Luke 5:30; Luke 15:2. And as the red heifer was expelled from the precincts of the camp, so was the Saviour cut off in no small measure during His Life from the fellowship of the chief representatives of the theocracy, and put to death outside Jerusalem between two thieves. Compare Hebrews 13:11-12.

19:3 Eleazar - Who was the second priest, and in some cases, the deputy of the high - priest. To him, not to Aaron, because this service made him unclean for a season, and consequently unfit for holy ministrations, whereas the high - priest was, as far as possibly he could, to be preserved from all sorts of defilement, fit for his high and holy work. Without the camp - Partly because it was reputed an unclean and accursed thing, being ladenwith the sins of all the people; and partly to signify that Christ should suffer without the camp, in the place where malefactors suffered.