3Jn 1:1. The clder. This term is explained at verse 1 of 2 John. There are several persons named Gaius in the New Testament. Thayer notes them in connection with certain passages, and at our verse lie says the following: "An unknown Christian, to whom the third epistle of John is addressed." Robinson's Lexicon, Funk and Wagnalls New Standard Bible Dictionary all favor the same identity. He was evidently John's convert, for in verse 4 he is included in "my children." Whom, I love in the truth is the same thing he says of the "lady" in the preceding book. It means his love for them is because of their devotion to the truth.
3Jn 1:2. This verse is similar to many passages where the grace of God is wished for the disciples. However, in this the writer is first expressing a wish for the physical health of his convert. He is interested in his spiritual welfare, of course, but he seems to know that Gaius is in satisfactory condition in that respect, which is indicated by the words as thy soul prospereth.
3Jn 1:3. Some brethren had brought a report of the conduct of Gaius which was favorable. That is the basis of his remark about his soul prospering.
3Jn 1:4. The joy over the faithfulness of leis convert is the kind of "reward" that he means in 2 John S. Being one of his converts John speaks of him as being among his children. (See explanation of this subject at 1Ti 1:2.)
3Jn 1:5. Doest faithfully denotes that whatever Gaius did he was in earnest about it; not halfhearted. He did his good deeds for others "heartily, as to the Lord, and not unto men" (Col 3:23). To brethren and to strangers is in keeping with Gal 6:10. Paul there says for disciples to "do good unto all men, especially to them who are of the household of faith."
3Jn 1:6. Have borne witness was done by the brethren mentioned in the preceding verse. They seem to have been traveling from place to place, or some of them were, which gave them an opportunity for making the report to John referred to. Gaius assisted these travelers in some way for their journey. After a godly sort means it was in the name of God and because of their work for Him.
3Jn 1:7. These traveling brethren were evidently engaged in spreading the Gospel, for the next verse speaks about being fellowhelpers to the truth. The Lord has "ordained that they which preach the gospel should live of the gospel" (1Co 9:14). Yet Paul refrained from such support in order that he might relieve the brethren of that pressure. The brethren of our verse did something similar, except they evidently made that concession to the people of the nations (Gentiles).
3Jn 1:8. Because of the aforesaid sacrifice John insists that the disciples should voluntarily assist them. Fel-10u:helpers to the truth. A man may not be able to preach the Gospel, but if he supports the man who does so he becomes a partner with him in the work and will be blessed of the Lord for his contribution.
3Jn 1:9. I wrote unto the church means the church of which Gaius was a member. This is indicated by some following statements in the book. John insists that he will come to the place to which he wrote the letter referred to, and at the same time trusts to see Gaius face to face. The fact that John wrote unto the church but that Diotrephes ignored the letter, indicates that the epistle was sent to this man as an elder of the congregation. That would be usual to send an official document to the officers, or at least in their care, as we read that Paul addressed his epistle to the church at Philippi to "the bishops and deacons" (Php 1:1). The epistle had something to do with John's proposed visit to the church, since he declares or implies that he is going to make the journey notwithstanding the opposition of. Diotrephes. This may raise a question in the mind of the reader whether it is right to visit a congregation against the authority of an elder. It is proper for an apostle to do so, for they were in the church before the elders. (See 1Co 12:28 where "governments" stands for the eldership.) Loveth to have the preeminence. This thirst for power among the elders is what resulted in the great falling away and development of the Church of Rome. Paul said in 2Th 2:7 that the mystery of this iniquity was already at work when he was writing, and he evidently was referring to such characters as Diotrephes. (See "General remarks at 2 Thessalonians 2 )
3Jn 1:10. John expects to come and when he does he will consider the deeds of Diotrephes, namely, his opposition to the apostle. Prating means to use false accusations against John in an effort to defend himself. Malicious words are the kind uttered with the intent of doing harm. Not content therewith is said because he not only opposed John, but opposed the brethren whom he sent to the church as messengers. He also forbade others who would have accepted the messengers, and if they showed friendship for the apostolic messengers, they were excluded from the church.
3Jn 1:11. This whole verse is a kindly exhortation for Gaius to continue in the good life that he is now following which will demonstrate that he is of God.
3Jn 1:12. This Demetrius is not found in any other place that I have seen. He was a disciple well spoken of by all who knew him. Of all, and of the truth itself. A man could have a good name without deserving it, but the report for Demetrius was a truthful one. John adds his testimony for the good name of this brother by saying we also bear record. It is probable that he was to be the bearer of this epistle.
3Jn 1:13. This has the same meaning as 2Jn 1:12.
3Jn 1:14. The usual friendly salutation from friends, just another affectionate title from the mind of the loving John. Greet the friends by name. This denotes a personal recognition of the faithful messengers who are coming to see the congregation.
Zerr, E.M. "Commentary on 3 John 1". E.M. Zerr's Commentary on Selected Books of the New Testament. https://www.studylight.org/commentaries/eng/znt/3-john-1.html. 1952.