Cautions them against deceivers :
There are a lot of smooth-talking charlatans loose in the world who refuse to believe that Jesus Christ was truly human, a flesh-and-blood human being. Give them their true title: Deceiver! Antichrist! And be very careful around them so you don’t lose out on what we’ve worked so diligently in together; I want you to get every reward you have coming to you.
Anyone who gets so progressive in his thinking that he walks out on the teaching of Christ, walks out on God. But whoever stays with the teaching, stays faithful to both the Father and the Son. If anyone shows up who doesn’t hold to this teaching, don’t invite him in and give him the run of the place. That would just give him a platform to perpetuate his evil ways, making you his partner. 2 John 1 : 7 – 11 (The Message)
The deceiver and his deceit are described: he brings some error concerning the person or office of the Lord Jesus. Such a one is a deceiver and an antichrist; he deludes souls, and undermines the glory and kingdom of the Lord Christ. Let us not think it strange, that there are deceivers and opposers of the Lord Christ’s name and dignity now, for there were such, even in the apostles’ times. The more deceivers and deceits abound, the more watchful the disciples must be. Sad it is, that splendid attainments in the school of Christ, should ever be lost.
The way to gain the full reward is, to abide true to Christ, and constant in religion to the end. Firm cleaving to Christian truth unites us to Christ, and thereby to the Father also; for they are one. Let us equally disregard such as abide not in the doctrine of Christ, and those who transgress his commands. Any who did not profess and preach the doctrine of Christ, respecting him as the Son of God, and salvation by him from guilt and sin, were not to be noticed and countenanced. Yet in obeying this command, we must show kindness and a good spirit to those who differ from us in lesser matters, but hold firmly the all-important doctrines of Christ’s person, atonement, and holy salvation.
Concluction :
I have a lot more things to tell you, but I’d rather not use paper and ink. I hope to be there soon in person and have a heart-to-heart talk. That will be far more satisfying to both you and me. Everyone here in your sister congregation sends greetings. 2 John 1 : 12, 13 (The Message)
The apostle refers many things to a personal meeting. Pen and ink were means of strengthening and comforting others; but to see each other is more so. The communion of saints should be maintained by all methods; and should tend to mutual joy. In communion with them we find much of our present joy, and look forward to happiness for ever.
Taken From Matthew Henry’s Concise Commentary.