Leviticus 8:6 And Moses brought Aaron and his sons, and washed them with water.
Important concept that continues into the New Testament times…
Leviticus 8:6 Gill
And Moses brought Aaron and his sons,…. To the laver which was in the court of the tabernacle
and washed them with water; to show that they should be clean that bear the vessels of the Lord, and offer the sacrifices of the people; all that are in public office in the house of God ought to have both clean hands and a pure heart, to hold the mystery of the faith in a pure conscience, and to be of a pure and holy conversation; and indeed all that are made kings and priests to God, as all the saints are, they are washed from their sins in the blood of Jesus, Rev 1:5.
Or from Matthew Henry…
Aaron and his sons were washed with water (Lev 8:6), to signify that they ought now to purify themselves from all sinful dispositions and inclinations, and ever after to keep themselves pure. Christ washes those from their sins in his own blood whom he makes to our God kings and priests (Rev 1:5, Rev 1:6); and those that draw near to God must be washed in pure water, Heb 10:22. Though they were ever so clean before and no filth was to be seen upon them, yet they must be washed, to signify their purification from sin, with which their souls were polluted, how clean soever their bodies were.
We also recall Jesus washing the disciples feet:
Joh 13:6 Then cometh he to Simon Peter: and Peter saith unto him, Lord, dost thou wash my feet?
Joh 13:7 Jesus answered and said unto him, What I do thou knowest not now; but thou shalt know hereafter.
Joh 13:8 Peter saith unto him, Thou shalt never wash my feet. Jesus answered him, If I wash thee not, thou hast no part with me.
Joh 13:9 Simon Peter saith unto him, Lord, not my feet only, but also my hands and my head.
Joh 13:10 Jesus saith to him, He that is washed needeth not save to wash his feet, but is clean every whit: and ye are clean, but not all.
Joh 13:11 For he knew who should betray him; therefore said he, Ye are not all clean.