“The focus of 2 John is living in the love of God in accordance with the truth of Jesus Christ. This love extends not only to God but to other people. It is also discerning; it does not “go on ahead” of biblical revelation (v. 9), and it does not lend aid to enemies of the gospel message (vv. 10–11). Instead, Christ’s followers “walk according to his commandments” (v. 6) and through faith “win a full reward” (v. 8).
The theme of 3 John is steadfastness in the face of opposition. The recipient of the letter, Gaius, faces a troublemaker named Diotrephes. By “walking in the truth” (vv. 3, 4), Christians can embrace and live out the apostolic message that John conveys in all his letters.” – Crossway Bibles. ESV Study Bible. Good News Publishers/Crossway Books
