Exodus 29:4 And Aaron and his sons thou shalt bring unto the door of the tabernacle of the congregation, and shalt wash them with water. - Free Bible Online

      4-9. Aaron and his sons thou shalt bring unto the door of the tabernacle--as occupying the intermediate space between the court where the people stood, and the dwelling-place of Israel's king, and therefore the fittest spot for the priests being duly prepared for entrance, and the people witnessing the ceremony of inauguration.
      wash them with water. And . . . take the garments--The manner in which these parts of the ceremonial were performed is minutely described, and in discovering their symbolical import, which indeed, is sufficiently plain and obvious, we have inspired authority to guide us. It signified the necessity and importance of moral purity or holiness (Isa 52:11; Joh 13:10; 2Co 7:1; 1Pe 3:21). In like manner, the investiture with the holy garments signified their being clothed with righteousness (Re 19:8) and equipped as men active and well-prepared for the service of God; the anointing the high priest with oil denoted that he was to be filled with the influences of the Spirit, for the edification and delight of the church (Le 10:7; Ps 45:7; Isa 61:1; 1Jo 2:27), and as he was officially a type of Christ (Heb 7:26; Joh 3:34; also Mt 3:16; 11:29).

JFB.