| Matthew Henry's Concise Commentary 1:9-12 Both the heart and mouth must be watched. The temper and spirit of Diotrephes was full of pride and ambition. It is bad not to do good ourselves; but it is worse to hinder those who would do good. Those cautions and counsels are most likely to be accepted, which are seasoned with love. Follow that which is good, for he that doeth good, as delighting therein, is born of God. Evil-workers vainly pretend or boast acquaintance with God. Let us not follow that which is proud, selfish, and of bad design, though the example may be given by persons of rank and power; but let us be followers of God, and walk in love, after the example of our Lord.
Pulpit CommentaryVer. 12. - Respecting Demetrius we know no more than is told us here. All that we can safely infer from what is stated is that he is a person of whom Gaius has not hitherto known much; otherwise this elaborate commendation would scarcely be necessary. Conjectures about him are (1) that he was the bearer of this Epistle to Gaius, - which is not improbable; (2) that he was a member of the same Church as Diotrephes, and had done good service in opposing him, - which is possible; (3) that he is the silversmith of Artemis (Acts 19:24), now "preaching the faith of which he once made havoc," - which is not probable. The name was a common one. It is not easy to determine the meaning of the statement that Demetrius hath the witness of all men, and of the truth itself. Perhaps it means that those who bore testimony to Demetrius were something more than a large body of unanimous human witnesses, strong as such testimony would be; in giving their witness they were guided by "the Spirit of truth." Or it may mean that the facts speak of themselves: as soon as Gaius knows Demetrius he will see that the universal commendation of him is amply justified. The true reading in what follows is, "and thou knowest that our witness is true" (comp. John 19:35; John 21:24). The calm confidence with which the writer asserts his authority, both over Diotrephes and also as a witness, confirms us in the belief that "the elder" is no less than the apostle.
Gill's Exposition of the Entire BibleDemetrius hath good report of all men, This man was of a quite different cast from Diotrephes, and therefore the apostle makes mention of him to Gaius, to be followed by him, and not the other; he was either the same with Demas, which is a contraction of this name, or the person that John sent from Ephesus with this letter: we read of an Ephesian of this name, Acts 19:24; though not the same person; or else one that also was a member of the same church with Gaius and Diotrephes; and he being kind and beneficent, obtained a good report of the generality of men, not only of the brethren, but of those that were without; for a liberal man is universally respected. The Syriac version adds, "and of the church itself"; as distinct from all men, or the generality of the men of the world: and of the truth itself; that is, whoever speaks truth must give him a good character, for this cannot be understood with any propriety of the Gospel, nor of Jesus Christ: yea, and we also bear record; or a testimony to the character of Demetrius; that is, I, John, the apostle, and the saints at Ephesus: and ye know that our record is true; faithful, and to be depended upon. The Alexandrian copy, and several others, read, "thou knowest", as does also the Vulgate Latin version, which seems most agreeable, since this epistle is directed to a single person; compare this with John 19:35; and it will give a further proof of this epistle being the Apostle John's.
Jamieson-Fausset-Brown Bible Commentary12. of all men—who have had opportunity of knowing his character. of the truth itself—The Gospel standard of truth bears witness to him that he walks conformably to it, in acts of real love, hospitality to the brethren (in contrast to Diotrephes), &c. Compare Joh 3:21 "He that doeth truth cometh to the light, that his deeds may be made manifest that they are wrought in God." we also—besides the testimony of "all men," and "of the truth itself." ye know—The oldest manuscripts read, "thou knowest."
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