Of purifying, Heb. of sin, i.e. for the expiation of sin. This water was mixed with the ashes of a red heifer, Numbers 19:9, which therefore may seem to have been prescribed before, though it be mentioned after; such kind of transplacings of passages being frequent in Scripture. Shave all their flesh; which external rite signified the cutting off their inordinate concupiscences of earthly things, and that singular purity of heart and life which is required in the ministers of God. See Isaiah 52:11 2 Timothy 2:21.
Related Commentaries of Numbers 8:7
Numbers 8:7
7 And thus shalt thou do unto them, to cleanse them: Sprinkle water of purifying upon them, and let them shavea all their flesh, and let them wash their clothes, and so make themselves clean.