Exodus 30:30

And thou shall anoint Aaron and his sons
Them alone, and not others, as Aben Ezra, who were typical of Christ anointed with the Spirit of God without measure, to his various offices of prophet, priest and King; and also of all the saints, who are anointed priests to God, to offer up spiritual sacrifices acceptable to God through Christ:

and consecrate them, that they may minister unto me in the priest's
office;
by anointing them, and by other rites mentioned in the preceding chapter; whereby they were set apart for that office, and were qualified for it, and had authority to exercise it.