1John 4:3

“"For whosoever does not confess that Jesus Christ has come in the flesh, is antichrist;" and whosoever does not confess the testimony of the cross, is of the devil; and whosoever perverts the oracles of the Lord to his own lusts, and says that there is neither a resurrection nor a judgment, he is the first-born of Satan. Wherefore, forsaking the vanity of many, and their false doctrines, let us return to the word which has been handed down to us from the beginning; "watching unto prayer," and persevering in fasting; beseeching in our supplications the all-seeing God "not to lead us into temptation," as the Lord has said: "The spirit truly is willing, but the flesh is weak."”

“We must after all this turn our attention to those scriptures also which forbid our belief in such a resurrection as is held by your Animalists (for I will not call them Spiritualists), that it is either to be assumed as taking place now, as soon as men come to the knowledge of the truth, or else that it is accomplished immediately after their departure from this life... Who has yet beheld Jesus descending from heaven in like manner as the apostles saw Him ascend, according to the appointment of the two angels? [Acts 1:11] Up to the present moment they have not, tribe by tribe, smitten their breasts, looking on Him whom they pierced. [John 19:37; Zechariah 12:10] No one has as yet fallen in with Elias; [Malachi 4:5] no one has as yet escaped from Antichrist; [1 John 4:3] no one has as yet had to bewail the downfall of Babylon. [Revelation 18:2] And is there now anybody who has risen again, except the heretic? He, of course, has already quitted the grave of his own corpse — although he is even now liable to fevers and ulcers; he, too, has already trodden down his enemies — although he has even now to struggle with the powers of the world. And as a matter of course, he is already a king — although he even now owes to Cæsar the things which are Cæsar's. [Matthew 22:21]”

“Well, but who is the man of sin, the son of perdition," who must first be revealed before the Lord comes; "who opposeth and exalteth himself above all that is called God, or that is worshipped; who is to sit in the temple of God, and boast himself as being God? " According indeed to our view, he is Antichrist; as it is taught us in both the ancient and the new prophecies, and especially by the Apostle John, who says that "already many false prophets are gone out into the world," the fore-runners of Antichrist, who deny that Christ is come in the flesh, and do not acknowledge Jesus (to be the Christ), meaning in God the Creator.”

“In like manner, in the passage, "If even an angel of heaven preach unto you any other gospel than that which we have preached unto you, let him be anathema," he calls attention to the artful influence of Philumene, the virgin friend of Apelles. Surely he is antichrist who denies that Christ has come in the flesh. By declaring that His flesh is simply and absolutely true, and taken in the plain sense of its own nature, the Scripture aims a blow at all who make distinctions in it.”

“But if we consider what the apostles thought about heretics, we shall find that they, in all their epistles, execrated and detested the sacrilegious wickedness of heretics. For when they say that "their word creeps as a canker," how is such a word as that able to give remission of sins, which creeps like a canker to the ears of the hearers? And when they say that there can be no fellowship between righteousness and un-righteousness, no communion between light and darkness, how can either darkness illuminate, or unrighteousness justify? And when they say that "they are not of God, but are of the spirit of Antichrist," how can they transact spiritual and divine matters, who are the enemies of God, and whose hearts the spirit of Antichrist has possessed? Wherefore, if, laying aside the errors of human dispute, we return with a sincere and religious faith to the evangelical authority and to the apostolical tradition, we shall perceive that they may do nothing towards conferring the ecclesiastical and saving grace, who, scattering and attacking the Church of Christ, are called adversaries by Christ Himself, but by His apostles, Antichrists.”

“If a spirit dissolves the divine-human unity of Christ and thinks that the pure Word of God is outside all flesh, and cannot really be a man, and states that everything done in his incarnation is a fantasy, then that spirit is not from God. But someone will say that there are many heretics who do accept the incarnation, the Montanists for instance. The answer to them is that just as no one says that Jesus is Lord except by the Holy Spirit, so the Montanists do not accept all the implications of incarnational belief. For those who say that Jesus is Lord but who do not follow his commandments do not have the Holy Spirit. Although they honor him with their lips, their hearts are far from him.”

“Thus then let us now also make the enquiry in the deeds not in the tongue. What is the spirit that is not from God? That "which denieth that Jesus Christ is come in the flesh." And what is the spirit that is from God? That "which confesseth that Jesus Christ is come in the flesh." Who is he that confesseth that Jesus Christ is come in the flesh? Now, brethren, to the mark! let us look to the works, not stop at the noise of the tongue. Let us ask why Christ came in the flesh, so we get at the persons who deny that He is come in the flesh. If thou stop at tongues, why, thou shalt hear many a heresy confessing that Christ is come in the flesh: but the truth convicteth those men. Wherefore came Christ in the flesh? Was He not God? Is it not written of Him, "In the beginning was the Word, and the Word was with God, and the Word was God?" Was it not He that did feed angels, is it not He that doth feed angels? Did He not in such sort come hither, that He departed not thence? Did He not in such sort ascend, that He forsook not us? Wherefore then came He in the flesh? Because it behooved us to have the hope of resurrection shown unto us. God He was, and in flesh He came; for God could not die, flesh could die; He came then in the flesh, that He might die for us. But how died He for us? "Greater charity than this hath no man, that a man lay down his life for his friends." Charity therefore brought Him to the flesh. Whoever therefore has not charity denies that Christ is come in the flesh. Here then do thou now question all heretics. Did Christ come in the flesh? "He did come; this I believe, this I confess." Nay, this thou deniest. "How do I deny? Thou hearest that I say it!" Nay, I convict thee of denying it. Thou sayest with the voice, deniest with the heart; sayest in words, deniest in deeds. "How," sayest thou, "do I deny in deeds?" Because the end for which Christ came in the flesh, was, that He might die for us. He died for us, because therein He taught much charity. "Greater charity than this hath no man, that a man lay down his life for his friends." Thou hast not charity, seeing thou for thine own honor dividest unity. Therefore by this understand ye the spirit that is from God. Give the earthen vessels a tap, put them to the proof, whether haply they be cracked and give a dull sound: see whether they ring full and clear, see whether charity be there. Thou takest thyself away from the unity of the whole earth, thou dividest the Church by schisms, thou rendest the Body of Christ. He came in the flesh, to gather in one, thou makest an outcry to scatter abroad. This then is the Spirit of God, which saith that Jesus is come in the flesh, which saith, not in tongue but in deeds, which saith, not by making a noise but by loving. And that spirit is not of God, which denies that Jesus Christ is come in the flesh; denies, here also, not in tongue but in life; not in words but in deeds. It is manifest therefore by what we may know the brethren. Many within are in a sort within; but none without except he be indeed without.”

“"And every spirit, qui solvit Christum, which does away with Christ that He came in the flesh, is not of God." A doing away in deeds is meant. What has he shown thee? "That denieth:" in that he saith, "doeth away" (or, "unmaketh"). He came to gather in one, thou comest to unmake. Thou wouldest pull Christ's members asunder. How can it be said that thou deniest not that Christ is come in the flesh, who rendest asunder the Church of God which He hath gathered together? Therefore thou goest against Christ; thou art an antichrist. Be thou within, or be thou without, thou art an antichrist: only, when thou art within, thou art hidden; when thou art without, thou art made manifest. Thou unmakest Jesus and deniest that He came in the flesh; thou art not of God. Therefore He saith in the Gospel: "Whoso shall break one of these least commandments, and shall teach so, shall be called least in the kingdom of heaven." What is this breaking? What this teaching? A breaking in the deeds and a teaching as it were in words. "Thou that preachest men should not steal, dost thou steal?" Therefore he that steals breaks or undoes the commandment in his deed, and as it were teaches so: "he shall be called least in the kingdom of heaven," i.e. in the Church of this present time. Of him it is said, "What they say do ye; but what they do, that do not ye."”

“"But he that shall do, and shall teach so, shall be called great in the kingdom of heaven." From this, that He has here said, fecerit, "shall do," while in opposition to this He has there said solverit, meaning non fecerit, "shall not do, and shall teach so" - to break, then, is, not to do - what doth He teach us, but that we should interrogate men's deeds, not take their words upon trust?”

“And every spirit that dissolves Jesus is not from God. He dissolves Jesus who denies either His divinity, or His soul, or His flesh, which the Catholic faith teaches that He truly has. He also dissolves Jesus who, by perversely interpreting or by perverse sight, corrupts the commands and words of Jesus. But also he who disturbs the unity of the holy Church, which Jesus came to gather, strives, as far as is in him, to dissolve Jesus. Nor is it surprising if such are not from God, who disband the works, words, or sacraments of God. For they are so far from God, that some of them who wished by evil doctrine to separate the divinity of Christ from human dispensation, have also erased this verse, where it is said, "And every spirit that dissolves Jesus is not from God," from this Epistle, lest their error be convicted by the authority of blessed John. Finally, Nestorius revealed that he did not know this sentence was inserted into the authentic copies, and therefore he did not fear to dissolve Jesus, and thus render himself foreign to God, saying that the blessed Virgin Mary was not the mother of God, but only of a man, such that he made another person of the man, another of the Deity; nor did he believe in one Christ in the Word of God and in flesh and soul, but preached separately another Son of God, another of man.”

“And this is the Antichrist of whom you have heard that he comes, etc. He comes with the imminent day of judgment, born into the world as that man more wicked than all others, the son of iniquity. And now he is already in the world, dwelling in the minds of those who resist Christ either by profession or by deed, without the remedy of repentance.”

“The Apostle says that the antichrist is already in the world; of course, not in person, but in the person of false prophets, false apostles, and heretics who precede and prepare his coming. And the antichrist himself will be a man bearing Satan within himself, "exalting himself above all that is called God or that is worshipped" (2 Thess. 2:4). This is also why he will forbid the worship of idols (which is what the Apostle meant by "that which is worshipped"), and will present himself alone as God.”