And Moses brought Aaron and his sons, and washed them with water.

Jamieson-Fausset-Brown Bible Commentary

6. Moses . washed them with water-At consecration they were subjected to entire ablution, though on ordinary occasions they were required, before entering on their duties, only to wash their hands and feet. This symbolical ablution was designed to teach them the necessity of inward purity, and the imperative obligation on those who bore the vessels and conducted the services of the sanctuary to be holy.

Matthew Henry's Concise Commentary

8:1-13 The consecration of Aaron and his sons had been delayed until the tabernacle had been prepared, and the laws of the sacrifices given. Aaron and his sons were washed with water, to signify that they ought to purify themselves from all sinful dispositions, and ever after to keep themselves pure. Christ washes those from their sins in his own blood whom he makes kings and priests to our God, Re 1:5,6; and those that draw near to God must be washed in pure water, Heb 10:22. The anointing of Aaron was to typify the anointing of Christ with the Spirit, which was not given by measure to him. All believers have received the anointing.