God had given Moses orders to consecrate Aaron and his sons to the priests’ office when he was on Mt. Sinai (Exodus 28-29), where we have also the particular instructions, he had now to do it. The Tabernacle had newly been set up and God was ready for Moses to consecrate the priests to being their duties.
He called the people together at the door of the tabernacle. The court of the tabernacle, being small, would only allow the principal men and elders of the congregation. The commission was read by Moses.
The ceremony performed according to the divine ritual. Aaron and his sons were washed with water to signify that they ought now to purify themselves from all sinful dispositions and inclinations, and ever after to keep themselves pure. They were clothed with holy garments, Aaron with his (8:7-9), which typified the dignity of Christ our great high priest, and his sons with theirs (8;13), which typified the decency of Christians.
Today, Christians are likewise washed in baptism to put on Christ. We continue to wear the robes of salvation. Those in heaven are spoken of as being “clothed with white robes” (Revelation 7:9). We are reminded over and over again that “holiness and purity” must be the description of the Christian life.