Third John is the shortest book in the Bible. Yet it is without doubt a very personal and vivid letter, an intimate communication between the writer and someone called Giaus.
Author
Second and 3 John are alike in many ways, one of which is the way the author identifies himself. Instead of using his name he uses the term or title, “the elder.” Like 2 John, 3 John gives no other information to identify the author. Tradition indicates that it was still John the apostle who authored this letter. A comparison of this epistle with the other writings of John will strongly supports that view.
Recipient
Again, 3 John is like 2 John. There is nothing in this book itself that serves as a clue to the date of its composition. Guesses range from the late 60s AD, to the 90s AD. The similarity of the contents of 3 John and 2 John would suggest a date of writing close to 2 John. If that is the case, most Bible expects estimate it was written most likely around 80 AD. Early Christian writers are unified in their testimony that the apostle John ended up in Ephesus. The book of Revelation does seem to confirm that.
The letter does not state which church Gaius belonged to, but his difficulties were chiefly concerned with a man named Diotrephes who had worked himself into a position of power in the church. John apparently commissioned several traveling teachers and preachers. A team of such teachers, led by Demetrius arrived with a letter of commendation from John, but a man named Diotrephes refused them and even refused to receive John’s letter (3 John 9). They returned to John and report both the hostility of Diotrephes and the hospitality of someone in the church called Gaius. John new Gaius well, he had led Gaius to Christ (3 John 4), and they were still close friends (3 John 1). Therefore, John wrote to this wealthy layman to encourage him to continue receiving missionaries despite the opposition of Diotrephes. He also announced his intention of personally visiting at some point to deal with the situation. Demetrius no doubt delivered the letter to Gaius.
Message
The subject of 3 John is love (3 John 5). In John’s thought, truth is the foundation of love (1 John 2: 3-11, esp. 2:4, 3:19; 2 John 4, 5; 3 John 3, 6). Hospitality is one expression of love. In 3 John, he contrasts Gaius loves others (3 John 6) and Diotrephes loved himself (3 John 9). The message is believers are to continue the practice of love in the form of hospitality.
Structure
Third John follows the formula of an ancient letter. It contains a salutation, prayer, a main text and ends with personal greetings and benediction.
I. Salutation 1
II. Prayer 2-4
III. The Body of the Letter 5-12
IV. Personal Greeting and Benediction 13-14
Purpose
The first purpose of 3 John is to encourage Gaius. Apparently, Gaius was wealthy (he entertained and shared hospitality a great deal), but apparently was not healthy (3 John 2). There was trouble at church: a strong-willed, headstrong man named Diotrephes was clearly repudiating the authority of the apostle John. He had suppressed his letter written to the church, refused to receive traveling teachers, and tried to prevent others from receiving them, even going so far as to excommunicate those who did. With his physical problems and the difficulties in his church, it would have been easy for Gaius to have stopped offering hospitality to missionaries. He could have always used his health as an excuse. Furthermore, to continue was to ask for trouble. John writes to encourage Gaius to continue doing what he was doing (3 John 5-6) and to tell him not to imitate Diotrephes (3 John 11); John saying he would deal with him when he arrived (3 John 10).
The second purpose of 3 John is to endorse Demetrius. Demetrius was likely the bearer of the letter, but, on the other hand, he was highly likely to have been one of the traveling teachers. Either way, he would need hospitality and support upon arrival. So, John writes to endorse him in the highest possible terms.
Summary:
John wrote to Gaius to encourage him to continue the practice of love in the form of hospitality and to endorse Demetrius. Hospitality is an important form of love this tells us.