The Book of 3 John does not directly name its author. The tradition from the earliest days of the church has been that John the Apostle was the author. There have been occasional doubts raised by those who thought it possible that this was written by another disciple of the Lord named John, but all the evidence points to the author being John the Apostle.
Date of Writing: The Book of 3 John would most likely have been written at about the same time as John's other letters, 1 and 2 John, likely between 85-95 A.D.
Purpose of Writing: 1. To commend and encourage his beloved co-worker Gaius in his ministry of hospitality to John's itinerant messengers who were going from place to place to preach the Gospel of Christ.
2. To indirectly warn and condemn the behavior of one Diotrephes, a dictatorial leader who had taken over one of the churches in the province of Asia, and whose behavior was directly opposed to all that the Apostle and his Gospel stood for.
3. To commend the example of Demetrius who was reported as having a good testimony from all.
Key Verses: 3 John verse 4, "I have no greater joy than to hear that my children walk in the truth."
3 John verse 11, "Beloved, do not imitate what is evil but what is good. He who does good is of God, but he who does evil has not seen God."
Brief Summary: John is writing with his usual strong emphasis on truth to this much loved brother in Christ, Gaius, a layman of some wealth and distinction in a city near Ephesus. He highly commends Gaius' care and hospitality to his messengers whose mission was to take the Gospel from place to place, whether they were known to him or were strangers. John exhorts him to continue to to do good and not to imitate evil, as in the example of Diotrephes. This man had taken over the leadership of a church in Asia and not only refused to recognize John's authority as an apostle but also to receive his letters and submit to his directions. He also circulated malicious slanders against John and excommunicated members who showed support and hospitality to John's messengers. Before he concludes his letter he also commends the example of Demetrius, of whom he has heard excellent reports.
Practical Application: John, as always, emphasizes the importance of walking in the truth of the Gospel. Hospitality, support and encouragement for our fellow Christians is one of the main precepts of the teachings of Jesus, and Gaius was obviously an outstanding example of this ministry. We should do the same whenever we can, welcoming visiting missionaries, preachers and strangers (as long as we are sure that they are true believers) not only to our churches but also to our homes, and offer them whatever support and encouragement they need.
We also need to be careful always to follow only the example of those whose words and actions are in line with the Gospel, and to be discerning enough to be able to be aware of those such as Diotrephes whose behavior is far from being like that which Jesus taught.