In none of these three epistles does the writer mention himself by name; but tradition assigns them to John, while the similarity of the language of these epistles and that of the fourth Gospel is strongly marked.
The first epistle emphasizes the fact that Jesus has come in the flesh and shows its bearing on the life of men. It was probably written after the Gospel, for it assumes in the reader a knowledge of the facts that the Gospel records. It also contains warnings against the dangers that beset a true faith in the literal incarnation of Jesus even before the end of the 1st century, both from teachers who claimed an authority independent of our Lord’s in the revelation of truth and from teachers who refused to acknowledge a real manifestation of the Godhead in human flesh.
The second epistle is closely connected with the first in the character of the false teaching it condemns (compare 2 Jn. 1:7 with 1 Jn. 4:2). The “elect lady” addressed in it is nameless. The writer of the letter styles himself the “Elder.”
In the third epistle the Elder refers to Gaius, Diotrephes, and Demetrius, all of whom are otherwise unknown to history.