Verse-by-verse analysis from Christians of the first millennium
[Clement of Alexandria] The second Epistle of John, which is written to Virgins, is very simple. It was written to a Babylonian lady, by name Electa, and indicates the election of the holy Church. He establishes in this Epistle that the following out of the faith is not without charity, and so that no one divide Jesus Christ; but only to believe that Jesus Christ has come in the flesh. For he who has the Son by apprehension in his intellect knows also the Father, and grasps with his mind intelligibly the greatness of His power working without beginning of time.
1 The elder unto the elect lady and her children, whom I love in the truth; and not I only, but also all they that have known the truth;
[Bede] The senior to the Lady elect. While some people doubt whether these two epistles are of the apostle John, through the fact, however, that they resemble the first one both in words and in a similar assertion of faith and charity against the heretics, they are proven to be of the apostle, not of the priest John. He writes to a certain Babylonian, who was called by her proper name Electa, advising her and her sons not to depart from the purpose of faith because of the heretics. Through this Electa the universal Mother Church is signified; through her sons the younger people begotten in faith by the Church. He writes therefore to the universal Church that there is no perfection of faith outside charity, and he execrates the heretics who divide Jesus Christ.
He goes so far in writing to the holy woman that he doesn't hesitate to call her "My lady" in writing, and he provides testimony about her sons that they walk in truth.
Not I only. As he is about to write against the heretics who have lost the truth, he says that one love for the saints is common to all who know the truth, so that by the similarity of Catholics he may deter them from the frequentation of the heretics. All the faithful agree in one truth, the heretics displease in their errors.
2 For the truth's sake, which dwells in us, and shall be with us forever.
3 Grace be with you, mercy, and peace, from God the Father, and from the Lord Jesus Christ, the Son of the Father, in truth and love.
[Bede] And from Christ Jesus the Son of the Father. There were at that time heretics who denied that Lord Jesus was the real Son of God, and he confutes them.
4 I rejoiced greatly that I found some of your children walking in truth, as we have received a commandment from the Father.
[Bede] I was exceeding glad. As if he said: What you have, keep it. Accept nothing else from the heretics, because I am glad of the things you have; I desire nothing more to be added to you for your salvation. Therefore, since I am glad of your good start, do not make (me) sad by your failure, because, as a careful guardian, I know everything that happens around you.
Walking in truth. Adam was put in the paradise to work it and to keep it. The work indicates the advance of the task carried out; the keeping indicates the state and steadiness of perfection itself.
5 And now I beseech you, lady, not as though I wrote a new commandment unto you, but that which we had from the beginning, that we love one another.
6 And this is love, that we walk after his commandments. This is the commandment, That, as you have heard from the beginning, you should walk in it.
7 For many deceivers are entered into the world, who confess not that Jesus Christ has come in the flesh. This is a deceiver and an antichrist.
[Irenaeus of Lyons] 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."
8 Look to yourselves, that we lose not those things which we have worked for, but that we receive a full reward.
[Bede] Look to yourselves, etc. Do not agree with such people, but rather pay attention to how you have been perfectly instructed to faith and constancy.
Reward, etc. That you may receive god fully with delight by persevering in the doctrine that was handed down to you, and by not agreeing with their error.
9 Whoever goes beyond, and abides not in the doctrine of Christ, has not God. He that abides in the doctrine of Christ, he has both the Father and the Son.
[Bede] Do not remain. If anyone separates himself from divine teaching, and from a right faith and conversation of the commandments of God, he separates himself from God, lest he have God. Through active and contemplative life, he who is the Creator of all becomes someone's God.
That persists. Stays in the evangelic doctrine, who knows and behaves according to it; parts from it, who knows and behaves differently.
10 If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed:
[Clement of Alexandria] He says, If any come unto you and bring not this doctrine, receive him not into your house, neither bid him God speed; for he that bids him God speed is partaker of his evil deeds. He forbids us to salute such, and to receive them to our hospitality. For this is not harsh in the case of a man of this sort. But he admonishes them neither to confer nor dispute with such as are not able to handle divine things with intelligence, lest through them they be seduced from the doctrine of truth, influenced by plausible reasons. Now, I think that we are not even to pray with such, because in the prayer which is made at home, after rising from prayer, the salutation of joy is also the token of peace.
[Cyprian] Said: John the apostle laid it down in his epistle, saying: "If any one come unto you, and have not the doctrine of Christ, receive him not into your house, and say not to him, Hail. For he that saith to him, Hail, partakes with his evil deeds."
[Bede] If any man come to you. As John in Ephesus was entering the baths to wash and saw Cherintus, he went out saying, "Let us flee from here, so that the baths themselves in which Cherintus, enemy of the truth, is washing, may not corrupt us." Therefore he did what he taught. For then the apostles and their disciples were using such caution in religious scrupulousness that they wouldn't even tolerate to share a word with one of those who had parted from the truth.
Receive him not. Because it looks like a sign of approbation of (his) error, indeed we say this to the friends whose works we like, and if by case you weren't deceived, yet others may be deceived through this friendship of yours, who would believe that you like them, and so would trust them.
11 For he that bids him God speed is partaker of his evil deeds.
12 Having many things to write unto you, I would not write with paper and ink: but I trust to come unto you, and speak face to face, that our joy may be full.
[Bede] More etc. Understand that this admonition will be very useful to you, because to its confirmation, I decided to come to you, and however I couldn't be completely silent in the meantime.
13 The children of your elect sister greet you. Amen.
Salute you. Just as he forbids saluting the adversaries of truth, so on the contrary does he salute the elect in the person of the elect.
The children of your sister Elect. Either literally, or perhaps the children of the church of the other metropolis. Grace be with you. This I say on my own part.