Who is a liar, but he who denieth that Jesus is the Christ? This is Antichrist, who denieth the Father, and the Son.

“Whosoever, therefore, declares that there is but one God, only so as to take away the divinity of Christ, is a devil, and an enemy of all righteousness. He also that confesseth Christ, yet not as the Son of the Maker of the world, but of some other unknown being, different from Him whom the law and the prophets have proclaimed, this man is an instrument of the devil. And he that rejects the incarnation, and is ashamed of the cross for which I am in bonds, this man is antichrist. Moreover, he who affirms Christ to be a mere man is accursed, according to the [declaration of the] prophet, since he puts not his trust in God, but in man. Wherefore also he is unfruitful, like the wild myrtle-tree.”

“John, moreover, brands that man as "a liar" who "denieth that Jesus is the Christ; "whilst on the other hand he declares that "every one is born of God who believeth that Jesus is the Christ." Wherefore he also exhorts us to believe in the name of His (the Father's, ) Son Jesus Christ, that "our fellowship may be with the Father, and with His Son Jesus Christ.”

“Let us see then how antichrists lie, because there is more than one kind of lying. "Who is a liar, but he that denieth that Jesus is the Christ?" One is the meaning of the word "Jesus," another the meaning of the word "Christ:" though it be one Jesus Christ our Saviour, yet "Jesus" is His proper name. Just as Moses was so called by his proper name, as Elias, as Abraham: so as His proper name our Lord hath the name "Jesus:" but "Christ" is the name of His sacred character. As when we say, Prophet, as when we say, Priest; so by the name Christ we are given to understand the Anointed, in whom should be the redemption of the whole people. The coming of this Christ was hoped for by the people of the Jews: and because He came in lowliness, He was not acknowledged; because the stone was small, they stumbled at it and were broken. But "the stone grew, and became a great mountain;" and what saith the Scripture? "Whosoever shall stumble at this stone shall be broken; and on whomsoever this stone shall come, it will grind him to powder." We must mark the difference of the words: it saith, he that stumbleth shall be broken; but he on whom it shall come, shall be ground to powder. At the first, because He came lowly, men stumbled at Him: because He shall come lofty to judgment, on whomsoever He shall come, He will grind him to powder. But not that man will He grind to powder at His future coming, whom He broke not when He came. He that stumbled not at the lowly, shall not dread the lofty. Briefly ye have heard it, brethren: he that stumbled not at the lowly, shall not dread the lofty. For to all bad men is Christ a stone of stumbling; whatever Christ saith is bitter to them. And how are they proved to be antichrists? By lying. "And who is a liar, but he that denieth that Jesus is the Christ?" Let us ask the heretics: where do you find a heretic that denies that Jesus is the Christ? See now, my beloved, a great mystery. Mark what the Lord God may have inspired us withal, and what I would fain work into your minds. Behold, they went out from us, and turned Donatists: we ask them whether Jesus be the Christ; they instantly confess that Jesus is the Christ. If then that person is an antichrist, who denies that Jesus is the Christ, neither can they call us antichrists, nor we them; therefore, neither they went out from us, nor we from them. If then we have not gone out one from another, we are in unity: if we be in unity, what means it that there are two altars in this city? what, that there are divided houses, divided marriages? that there is a common bed, and a divided Christ? For if all be asked, all with one mouth confess that Jesus is the Christ. Let the tongue keep still for a little while, ask the life. If we shall find this, if the Scripture itself shall tell us that denial is a thing done not only with the tongue, but also with the deeds, then assuredly we find many antichrists, who with the mouth profess Christ, and in their manners dissent from Christ. Where find we this in Scripture? Hear Paul the Apostle; speaking of such, he saith, "For they confess that they know God, but in their deeds deny Him." We find these also to be antichrists: whosoever in his deeds denies Christ, is an antichrist. I listen not to what he says, but I look what life he leads. Works speak, and do we require words? For where is the bad man that does not wish to talk well? But what saith the Lord to such? "Ye hypocrites, how can ye speak good things, while ye are evil?" Your voices ye bring into mine ears: I look into your thoughts. I see an evil will there, and ye make a show of false fruits. I know what I must gather, and whence; I do not "gather figs of thistles," I do not gather "grapes of thorns;" for "every tree is known by its fruit." A more lying antichrist is he who with his mouth professes that Jesus is the Christ, and with his deeds denies Him. A liar in this, that he speaks one thing, and does another. Now therefore, brethren, if deeds are to be questioned, not only do we find many antichrists gone out; but many not yet manifest, who have not gone out at all. For as many as the Church hath within it that are perjured, defrauders, addicted to black arts, consulters of fortune-tellers, adulterers, drunkards, usurers, boy-stealers, and all the other vices that we are not able to enumerate; these things are contrary to the doctrine of Christ, are contrary to the word of God. Now the Word of God is Christ: whatever is contrary to the Word of God is in Antichrist. For Antichrist means, "contrary to Christ." And would ye know how openly these resist Christ? Sometimes it happens that they do some evil, and one begins to reprove them; because they dare not blaspheme Christ, they blaspheme His ministers by whom they are reproved: but if thou show them that thou speakest Christ's words, not thine own, they endeavor all they can to convict thee of speaking thine own words, not Christ's: if however it is manifest that thou speakest Christ's words, they go even against Christ, they begin to find fault with Christ: "How," say they, "and why did He make us such as we are?" Do not persons say this every day, when they are convicted of their deeds? Perverted by a depraved will, they accuse their Maker.”

“Who is a liar, but he that denieth that Jesus is the Christ?.... Or that very Christ, and true Messiah, who was spoken of by all the prophets, since the beginning of the world, and so much, and so long desired by the Old Testament saints: he that denies that Jesus of Nazareth is the Messiah of the prophets, is not indeed the only liar in the world, but he is the greatest of liars; this is a consummate lie, being opposed to a glaring truth, to a fact clear an indisputable; and which rests not merely on the testimony of Jesus, who is truth itself, and who, in express words, more than once, declared and asserted himself to be the Christ; but all the characters of the Messiah, everything that is said of him in the Prophets, meet in Jesus, and the miracles which were done by him are flagrant proofs and undeniable evidences of his being the Christ of God; and all the apostles believed, and were sure that he was Christ, the Son of the living God: to which may be added the testimony of John, who was sent, and came to bear witness of him, and did; and who was a prophet, and a man of great probity and integrity. But there was a greater witness than he; even God himself, by a voice from heaven, bore a testimony to him; and angels, at his incarnation, declared him to be the Saviour, which is Christ the Lord; yea, the devil himself, who is a liar, and the father of ties in other things, knew and owned Jesus to be the Christ; so that those that deny him are the worst of liars, even worse than the devil himself. This may have regard not only to the Jews, that deny Jesus to be the Messiah, but chiefly to such who went by the name of Christians; who denied either his proper deity, or real humanity, as Ebion and Cerinthus, which was denying him to be the God-man, the Mediator, and Messiah; and is true of all such that deny him in any of his offices, or in things relating to them, as his Gospel, and any of the peculiar doctrines of it, delivered by him, and so deny his prophetic office; or any of his ordinances, institutions, and appointments, as lawgiver in his house, and King of saints, and so deny him in his kingly office; or reject him as the alone Saviour, joining their own works with him, in the business of salvation, and oppose his sacrifice and satisfaction, and despise his imputed righteousness, and so deny him in his priestly office. Now these are some of the liars, and these some of the doctrinal lies, which are not of the truth, as in 1Jo_2:21. He is antichrist that denieth the Father and the Son: that denies the Father of Christ to be the Creator of the world, but asserts that it was made by angels, as some ancient heretics did; or that the Father of Christ is not the God of the Old Testament, as Marcion; or that denies that God is the Father of Christ, and that Christ is the Son of God; who will not allow that there is any such relation in nature between them; who affirm that Christ is only the Son of God by adoption, or because of his love to him, or because of his incarnation and resurrection from the dead; or that he is not his true and proper Son, only in a figurative and metaphorical sense; that he is not the natural and eternally begotten Son of God, only by office, and as Mediator, and that God is only his Father, as having installed him into an office; or he that denies that these two are distinct from each other, but affirms that Father is the Son, and the Son is the Father, and so confounds them both, and, by confounding both, denies that there are either Father or Son; and all such persons are antichrists, or opposers of Christ.”

“Who is a liar but he that denieth that Jesus is the Christ? - Here we see some of the false doctrines which were then propagated in the world. There were certain persons who, while they acknowledged Jesus to be a Divine teacher, denied him to be the Christ, i.e. the Messiah. He is antichrist, that denieth the Father and the Son, - He is antichrist who denies the supernatural and miraculous birth of Jesus Christ, who denies Jesus to be the Son of God, and who denies God to be the Father of the Lord Jesus; thus he denies the Father and the Son. The Jews in general, and the Gnostics in particular, denied the miraculous conception of Jesus; with both he was accounted no more than a common man, the son of Joseph and Mary. But the Gnostics held that a Divine person, Aeon, or angelical being, dwelt in him; but all things else relative to his miraculous generation and Divinity they rejected. These were antichrists, who denied Jesus to be the Christ.”

“He who denieth that Jesus is the Christ? He is antichrist: is in a special manner an adversary of Christ and the Christian religion, when he denies Jesus to be the Messias, or to have been from eternity the true Son of God. — He who denieth him to be the Son, neither hath he the Father. He who denies either of these truths denieth both. He who denies the Son of God to be the eternal Son, denies the Father to be the eternal Father. (Witham)”

“a liar--Greek, "Who is the liar?" namely, guilty of the lie just mentioned (Jo1 2:21). that Jesus is the Christ--the grand central truth. He is Antichrist--Greek, "the Antichrist"; not however here personal, but in the abstract; the ideal of Antichrist is "he that denieth the Father and the Son." To deny the latter is virtually to deny the former. Again, the truth as to the Son must be held in its integrity; to deny that Jesus is the Christ, or that He is the Son of God, or that He came in the flesh, invalidates the whole (Mat 11:27).”