Exposition of the Old and New Testament, by John Gill, [1746-63], at sacred-texts.com
This epistle was written by the Apostle John, who calls himself an "elder", as in the preceding, and is inscribed to a friend of his, whom he mentions by name, and expresses a very great affection for, on account of his steady adherence to the truths of the Gospel, Jo3 1:1; he wishes him bodily health equal to that prosperity of soul he was indulged with, Jo3 1:2; congratulates him upon the testimony the brethren that came from him gave him of the truth being in him, and of his walking in it, and upon hearing that his children also trod in the same path, Jo3 1:3; commends him for his hospitality and charity, of which testimonies were given before the church; and encourages him to go on doing the same acts of beneficence, since it was to such persons that went forth for the sake of Christ, and preaching in his name, and had nothing of the Gentiles for so doing; wherefore they ought to be received, and entertained by those of ability, that they might be fellow helpers to the truth with them, Jo3 1:5. He complains of Diotrephes as a proud, haughty, and overbearing man in the church, where Gaius was a member, who would neither receive the letters the apostle sent, nor the brethren that came with them; nay, forbid them that would, and cast them out of the church for it, and prated against them with malicious words, whom he threatens to remember when he himself should come thither, Jo3 1:9; wherefore he exhorts Gaius not to follow such an ill example, but that which is good in any person; since he that does good appears to be of God, and he that does evil, it looks as if he had never known him, Jo3 1:11. And particularly he recommends Demetrius, who had a good report of all men, and of the truth itself, and had a testimony from the apostle, and those that were with him, which was known to be a true one, Jo3 1:12. But though he had many things to say, both of one, and of the other, he determines to write no more at present, hoping he should shortly see him, and personally converse together; and closes the epistle with his own good wish, and with mutual salutations of friends, Jo3 1:13.