Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
The Second and Third Epistles of John insist on the truth. The Second warns the faithful against the reception of those who do not teach the doctrine of Christ, especially the truth respecting the Person of Christ. The Third encourages believers to receive and help those who teach it. Accordingly they both (and the Second especially) lay stress on "the truth."
The apostle loved this elect lady, "in the truth;" as did also all those who had known the truth, and that for the truth's sake. He wished her blessing in truth and in love. He rejoiced that he had found some who were her children walking in the truth. He desired that there should be mutual love among Christians, but this was love, that they should keep the commandments; for many deceivers were come into the world. Now whosoever transgressed, and did not abide in the doctrine of Christ, had not God. He ends his epistle, of which we have given an almost complete summary, by exhorting this lady, in case any one should come and not bring this doctrine, not to receive him into her house, nor say to him, "God bless you, or be with you," or "I salute you." For to do so would be to make herself a partaker in the evil he was doing.
The false doctrine which was abroad at that moment was the denial of the truth of Christ come in the flesh; but the apostle says in a general way that, if any one transgressed and did not abide in the doctrine of Christ, he had not God.
We learn several important things in this little epistle. The mission of a man who went about preaching was never brought into question, but the doctrine which he brought; if he brought sound doctrine he was welcome.
A woman having the word as this epistle, for example was capable of judging his doctrine, and responsible to do so. Inexorable rigour was to be maintained, if the doctrine as to the Person of Christ was touched. The door was to be shut against whoever falsified it. They were not even to say to him, "I salute you;" for they who did so became partakers of his evil work. It would be to help on the deceits of Satan.
Moreover the semblance of love which does not maintain the truth, but accommodates itself to that which is not the truth, is not love according to God. It is the taking advantage of the name of love in order to help on the seductions of Satan. In the last days the test of true love is the maintenance of the truth. God would have us love one another; but the Holy Ghost, by whose power we receive this divine nature, and who pours the love of God into our hearts is the Spirit of truth; and His office is to glorify Christ. Therefore it is impossible that a love which can put up with a doctrine that falsifies Christ, and which is indifferent to it, can be of the Holy Ghost still less so, it such indifference be set up as the proof of that love.
The doctrine of the reward and crown of glory, which the labourer possesses in the fruits of his ministry, is presented in a very strong light in Verse 8 (Jo2 1:8) This Second Epistle puts Christians on their guard against all that is equivocal with respect to the person of Christ; and exhorts to an unwavering firmness on this point.