A.T. Robertson Commentary 1 John 2:20

"And ye have an anointing from the Holy One, and ye know all the things." — 1 John 2:20 (ASV)

Anointing (χρισμα). Old word for result (ματ) and for the material, from χριω, to anoint, perhaps suggested by the use of αντιχριστο in verse 18. Christians are "anointed ones," χριστο in this sense, with which compare Ps 105:15 "Touch not my anointed ones" (μη αψησθε των χριστων μου). These antichrists posed as the equals of or even superior to Christ himself. But followers of Christ do have "the oil of anointing" (το ελαιον του χρισματος, Exodus 29:7), the Holy Spirit. This word in the N.T. only here and verse 27. Later the term was applied to baptism after baptismal remission came to be taught (Tertullian, etc.).

From the Holy One (απο του αγιου). They receive this anointing of the Holy Spirit from the Anointed One, Jesus Christ (the Holy One). Cf. John 6:69; Acts 3:14.

And ye know all things (κα οιδατε παντα). But the best MSS. read παντες rather than παντα, "Ye all know it." This anointing is open to all Christians, not just a select few.