Adam Clarke on Exodus 30:30

Thou shalt anoint Aaron and his sons - For the reason of this anointing, see Clarke's note on Exo 29:7. It seems that this anointing oil was an emblem of Divine teaching, and especially of those influences by which the Church of Christ was, in the beginning, guided into all truth; as is evident from the allusion to it by St. John: "Ye have an unction from the Holy One, and ye know all things. The anointing which ye have received from him abideth in you, and ye need not that any man teach you; but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in Him; 1Jn 2:20, 1Jn 2:27.