Not all of them, but only those who succeed him in the high priest's office, as appears from Exodus 40:15 Leviticus 4:3,5,16; Exodus 16:32, Exodus 21:10. This anointing of them signified both God's election or calling them to this office, and the inward qualifications requisite for it, to wit, the gifts and graces of the Holy Ghost, which are oft designed by this word of anointing, as Isaiah 61:1 Daniel 9:24 1 John 2:27, and the solemn setting apart of Christ, the true High Priest, for the mediatorial office.
Related Commentaries of Exodus 30:30
Exodus 30:30
30 And thou shalt anoint Aaron and his sons, and consecrate them, that they may minister unto me in the priest's office.