1:7-11 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.
11. By wishing a false brother or teacher "God (or 'good') speed," you imply that he is capable as such of good speed and joy (the literal meaning of the Greek), and that you wish him it while opposing Christ; so you identify yourself with "his evil deeds." The Greek of "partaker" is "having communion with." We cannot have communion with saints and with Antichrist at the same time. Here we see John's naturally fiery zeal directed to a right end. Polycarp, the disciple of John, told contemporaries of Irenæus, who narrates the story on their authority, that on one occasion when John was about to bathe, and heard that Cerinthus, the heretic, was within, he retired with abhorrence, exclaiming, Surely the house will fall in ruins since the enemy of the truth is there.