Irenaeus

In his own words on 1 John

• 1 John 1:6

  ...the apostles who did also write the Gospel, in which they recorded the doctrine regarding God, pointing out that our Lord Jesus Christ is the truth, and that no lie is in Him. As also David says, prophesying His birth from a virgin, and the resurrection from the dead, "Truth has sprung out of the earth." The apostles, likewise, being disciples of the truth, are above all falsehood; for a lie has no fellowship with the truth, just as darkness has none with light, but the presence of the one shuts out that of the other. Our Lord, therefore, being the truth, did not speak lies...

  Against Heresies Book III

• 1 John 2:1

  This Spirit, again, He did confer upon the Church, sending throughout all the world the Comforter from heaven, from whence also the Lord tells us that the devil, like lightning, was cast down. Wherefore we have need of the dew of God, that we be not consumed by fire, nor be rendered unfruitful, and that where we have an accuser there we may have also an Advocate, the Lord commending to the Holy Spirit His own man, who had fallen among thieves, whom He Himself compassionated, and bound up his wounds, giving two royal denaria; so that we, receiving by the Spirit the image and superscription of the Father and the Son, might cause the denarium entrusted to us to be fruitful, counting out the increase [thereof] to the Lord.

  Against Heresies Book III

• 1 John 2:18

  The Gospel, therefore, knew no other son of man but Him who was of Mary, who also suffered; and no Christ who flew away from Jesus before the passion; but Him who was born it knew as Jesus Christ the Son of God, and that this same suffered and rose again, as John, the disciple of the Lord, verifies, saying: "But these are written, that ye might believe that Jesus is the Christ, the Son of God, and that believing ye might have eternal life in His name," -foreseeing these blasphemous systems which divide the Lord, as far as lies in their power, saying that He was formed of two different substances. For this reason also he has thus testified to us in his Epistle: "Little children, it is the last time; and as ye have heard that Antichrist doth come, now have many antichrists appeared; whereby we know that it is the last time. They went out from us, but they were not of us; for if they had been of us, they would have continued with us: but [they departed], that they might be made manifest that they are not of us. Know ye therefore, that every lie is from without, and is not of the truth. Who is a liar, but he that denieth that Jesus is the Christ? This is Antichrist."

  Against Heresies Book III

• 1 John 4:1

  All, therefore, are outside of the [Christian] dispensation, who, under pretext of knowledge, understand that Jesus was one, and Christ another, and the Only-begotten another, from whom again is the Word, and that the Saviour is another, whom these disciples of error allege to be a production of those who were made Aeons in a state of degeneracy. Such men are to outward appearance sheep; for they appear to be like us, by what they say in public, repeating the same words as we do; but inwardly they are wolves. Their doctrine is homicidal, conjuring up, as it does, a number of gods, and simulating many Fathers, but lowering and dividing the Son of God in many ways. These are they against whom the Lord has cautioned us beforehand; and His disciple, in his Epistle already mentioned, commands us to avoid them, when he says: "For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. Take heed to them, that ye lose not what ye have wrought." And again does he say in the Epistle: "Many false prophets are gone out into the world. Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God; and every spirit which separates Jesus Christ is not of God, but is of antichrist." These words agree with what was said in the Gospel, that "the Word was made flesh, and dwelt among us." Wherefore he again exclaims in his Epistle, "Every one that believeth that Jesus is the Christ, has been born of God;" knowing Jesus Christ to be one and the same, to whom the gates of heaven were opened, because of His taking upon Him flesh: who shall also come in the same flesh in which He suffered, revealing the glory of the Father.

  Against Heresies Book III

• 1 John 5:1

  All, therefore, are outside of the [Christian] dispensation, who, under pretext of knowledge, understand that Jesus was one, and Christ another, and the Only-begotten another, from whom again is the Word, and that the Saviour is another, whom these disciples of error allege to be a production of those who were made Aeons in a state of degeneracy. Such men are to outward appearance sheep; for they appear to be like us, by what they say in public, repeating the same words as we do; but inwardly they are wolves. Their doctrine is homicidal, conjuring up, as it does, a number of gods, and simulating many Fathers, but lowering and dividing the Son of God in many ways. These are they against whom the Lord has cautioned us beforehand; and His disciple, in his Epistle already mentioned, commands us to avoid them, when he says: "For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist. Take heed to them, that ye lose not what ye have wrought." And again does he say in the Epistle: "Many false prophets are gone out into the world. Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God; and every spirit which separates Jesus Christ is not of God, but is of antichrist." These words agree with what was said in the Gospel, that "the Word was made flesh, and dwelt among us." Wherefore he again exclaims in his Epistle, "Every one that believeth that Jesus is the Christ, has been born of God;" knowing Jesus Christ to be one and the same, to whom the gates of heaven were opened, because of His taking upon Him flesh: who shall also come in the same flesh in which He suffered, revealing the glory of the Father.

  Against Heresies Book 3

• 1 John 5:6

  Moreover, how could the Lord, with any justice, if He belonged to another father, have acknowledged the bread to be His body, while He took it from that creation to which we belong, and affirmed the mixed cup to be His blood? And why did He acknowledge Himself to be the Son of man, if He had not gone through that birth which belongs to a human being? How, too, could He forgive us those sins for which we are answerable to our Maker and God? And how, again, supposing that He was not flesh, but was a man merely in appearance, could He have been crucified, and could blood and water have issued from His pierced side? What body, moreover, was it that those who buried Him consigned to the tomb? And what was that which rose again from the dead?

  Against Heresies Book IV