The word translated ‘unction’ here is ‘anointing.’ John reminds his readers of an anointing they have from the Holy One (Christ). This is not some ‘Second Blessing’ anointing that they were to seek upon conversion to Christ, but a blessed anointing they had already in, by, and through Him. Of what anointing is he speaking?
1. This is primarily a term that pertains to Christ himself. The title ‘Christ’ means ‘The Anointed One,’ Isa. 61:1; Acts 4:27. God the Father chose Him and set Him apart as Prophet, Priest, and King. In the Old Testament, such men were set apart by anointing. In Christ, all three offices converge. God speaks to no one in saving mercy but through His Son, THE PROPHET, Acts 3:22. God receives no sinner in any other way than Christ’s work and sacrifice as THE PRIEST, Hebrews 8:1. God causes all sinners, for whom Christ gave His life as a ransom, to bow to Him as KING, Rev. 15:3.
2. To have an anointing from Him as the Holy One means that the righteousness that He worked out as THE ANOINTED One of God, was imputed to everyone for whom He died, WHEN He died, Rom. 5: 9, 10. Christ is that Holy One in whom, by whom, and for whom His people were chosen, redeemed, justified, and sanctified, I Cor. 1:30. Because of His finished work, accepted of the Father, His people enjoy ALL spiritual blessings in Him (Ephesians 1:3).
3. They ‘know ALL things,’ not that they don’t need to be taught, but in that the Spirit of God having revealed Christ in them, causes them to see in HIM and His finished work, all things fulfilled pertaining to their forgiveness and justification before God. They are contrasted with those who walk away from the truth (v.19) by following their own fleshly devices, or a doctrine contrary to Christ, either by adding to, or taking away from salvation full and complete in Him. Their anointing is that when He died and rose again, they were in Him, therefore His anointing is theirs. In time, the Spirit brings them, by faith, to enjoy the blessing of this anointing they have already from Christ, by grace. Even as He is the complete satisfaction of the Father for them, so He is their complete satisfaction before the Father. Believers neither need nor want anything more!
-- Ken Wimer, in Shreveport Grace Church Bulletin