2:18-23 Every man is an antichrist, who denies the Person, or any of the offices of Christ; and in denying the Son, he denies the Father also, and has no part in his favour while he rejects his great salvation. Let this prophecy that seducers would rise in the Christian world, keep us from being seduced. The church knows not well who are its true members, and who are not, but thus true Christians were proved, and rendered more watchful and humble. True Christians are anointed ones; their names expresses this: they are anointed with grace, with gifts and spiritual privileges, by the Holy Spirit of grace. The great and most hurtful lies that the father of lies spreads in the world, usually are falsehoods and errors relating to the person of Christ. The unction from the Holy One, alone can keep us from delusions. While we judge favourably of all who trust in Christ as the Divine Saviour, and obey his word, and seek to live in union with them, let us pity and pray for those who deny the Godhead of Christ, or his atonement, and the new-creating work of the Holy Ghost. Let us protest against such antichristian doctrine, and keep from them as much as we may.

21. but because ye know it, and that, &c.—Ye not only know what is the truth (concerning the Son and the Father, 1Jo 2:13), but also are able to detect a lie as a thing opposed to the truth. For right (a straight line) is the index of itself and of what is crooked [Estius]. The Greek is susceptible of Alford's translation, "Because ye know it, and because no lie is of the truth" (literally, "every lie is excluded from being of the truth"). I therefore wrote (in this Epistle) to point out what the lie is, and who the liars are.