Charles Ellicott Commentary Numbers 8:7

"And thus shalt thou do unto them, to cleanse them: sprinkle the water of expiation upon them, and let them cause a razor to pass over all their flesh, and let them wash their clothes, and cleanse themselves." — Numbers 8:7 (ASV)

Water of purifying. — Literally, water of sin, or, of sin-offering (Hebrew, hattath). As in the case of the holy water, to which reference is made in Numbers 6:17, so here also there is no explanation given of the particular water to be used in cleansing the Levites. The bullock appointed to be offered as a sin-offering at the consecration of Aaron and his sons (Exodus 29:14; Leviticus 8:14) is described by the same word used here (in the Authorized Version, sin-offering); and in Leviticus 4:14, the sacrifice appointed to be offered for the expiation of sin (in the Authorized Version, the sin) is also spoken of under the same name. So also is the sin-offering of the Levites in Numbers 8:8 of this chapter.

The sin-water evidently denotes the water appointed to be used in the purification of sin; and the reference is probably to the water kept in the brazen laver in front of the Tabernacle. It is possible, however, that some direction not recorded here may have been given regarding putting the ashes of the sin-offering into water. (Compare Numbers 19:9, where the water of purification is described under the same name: it is a purification for sin. Literally, it is hattath.) In this case, however, the sin-offering, which is not mentioned until Numbers 8:8, must have been sacrificed before the sprinkling.

Let them shave all their flesh. — Literally, cause the razor to pass over all their flesh. A different word is used in Leviticus 14:8-9 to denote the more complete removal of the hair which was required at the cleansing of the leper.

And let them wash their clothes. — The bodies of the priests were washed at their consecration (Leviticus 14:8–9), and those of the lepers at their cleansing (Leviticus 8:6). However, the Levites, who were not brought into such immediate contact with the holy things as the priests, were only required to wash their clothes. This was an ordinary preparation for divine worship (Exodus 19:10).