And in these three letters the same authorial seal is discernible, and for this reason it has always been almost universally accepted that they come from the same hand and mind. For this reason, the three have remained inseparable from each other, constituting a class of their own among all the letters of the New Testament. The author of these belongs to the eyewitnesses and listeners of the Lord, and he calls himself "the elder," and according to the unanimous tradition of the Church he is the evangelist John.

The first of these letters, quite extensive, was written by the Apostle on account of the danger created in the Church by certain false teachers, who are characterized as precursors and instruments of the antichrist, and are called antichrists by the Apostle. These heretics denied that Jesus is the Son of God and that He became man and suffered for us in truth and in reality. For this reason, the Apostle wrote this letter, most likely from Ephesus, at about the same time as he wrote the Gospel. He set as its main purpose to support his spiritual children in the known faith and in unbroken communication with the eyewitnesses of the Word of life.

The second letter, being short, is addressed to "the chosen lady" and concludes with a brief greeting on behalf of the children of the sister of this chosen lady. According to the most probable opinion, by this phrase the Evangelist metaphorically implies a certain local Church and therefore argues that it is more natural that the children of the other chosen lady, who send the greetings, are also presented as members of some other local Church. And this letter was written on account of the danger from false teachers, with the purpose of securing the faithful to whom the letter was sent, until the Evangelist would have the opportunity to visit them in person. It seems that this too was sent from Ephesus after the first Catholic letter.

And the third epistle is as short as the second. It was written by some of the brethren who were traveling about preaching the Gospel, and whom the divine Apostle recommends to the hospitality of each Christian. It is addressed to a certain Gaius, to whom the Apostle himself recommends these travelers, complaining at the same time about a certain Diotrephes, who, opposing the Apostle, persecuted those who came from him and expelled from the Church all who would receive them.

The letter was written during the last years of the Apostle's life, most likely from Ephesus.