Anointing in the holy Scriptures is either material, with oil, or spiritual, with the Holy Spirit.
At his baptism Jesus was baptized with the Spirit, the first person in human history to receive this highest honor possible for men to receive or for heaven to bestow. For in the Old Testament, anointing was the official inauguration into three of the highest offices of the Hebrew nation — king and prophet (1 Kings 19:16), high priest (Lev. 16:32), and king (1 Sam. 9:16). These three offices were typical of a great personality to come in the latter days, called the Messiah, the Christ, or the Anointed One (Psa. 2:2; Dan. 9:25, 26; Luke 4:18). The nature of this anointing is foretold as spiritual: "The Spirit of the Lord is upon me: because the Lord hath anointed me to preach good tidings to the meek." Jesus of Nazareth appropriated this prophecy when he said, "This day is this Scripture fulfilled in your ears." This spiritual anointing being one of his chief credentials, the fact is recorded in John 1:32, 33; Acts 4:27; 10:38.
But the astonishing fact that this unique honor may be shared by all his true disciples, however humble and obscure, down through all the coming generations, was not clearly revealed in the Gospels. It was one of those truths which even his apostles were not able to understand till they had received the anointing itself on the day of Pentecost. Says Paul to the Corinthians (2 Cor. 1:21), "Now he which stablisheth us with you in Christ, and hath anointed us, is God." More exact is Meyer: "He who makes us steadfast after he has anointed us." This shows the relation of this anointing to the development and stability of the Christian character.
To anoint the eyes with eye-salve is a figurative description of that instantaneous purging of the inward eye of the film of inbred sin by the incoming of the Sanctifier, imparting the power of clear spiritual perception (Rev. 3:18). All that is said about the anointing as the privilege of all believers occurs very naturally after Pentecost.
Hence the Greek χρῖσμα (chrisma) is not found in the four Gospels; and it occurs in the New Testament only three times, and all of them in the First Epistle of John: "But ye have an unction from the Holy One, and ye know all things." — 2:20.
In my limitation of "all things" to all spiritual truths, "necessary to life and godliness," I was once criticized by Gilbert Haven, editor of Zion's Herald. He said that my exclusion of philosophy and science from the "all things" was a needless limitation, since Christianity is the tree on whose branches all kinds of knowledge are found in perfection. There is a large kernel of truth in the criticism of my translated friend. The most Christian nations are the most scholarly, inventive, and progressive. Those who have the least of God's Spirit have the least intelligence. Many an individual. quickened by the Holy Ghost, has been aroused from mental stagnation to an inquiry after truth, which has led him through the whole range of biblical truth and its out-branchings into all the sciences and philosophies. The unction of the Holy Spirit is the highway to all knowledge. This is especially true of an insight into theology. Says that seraphic Scotchman, Samuel Rutherford, "If you would be a deep divine, I recommend to you sanctification"; i.e., the anointing.
— edited from Half-Hours With St. Paul Chapter 21.