III John is the shortest book in the Bible and is very personal and vivid. It was written by the apostle John in the late 1st century to Gaius, a member of one of his churches. The epistle contrasts the responses of two men to traveling teachers sent out by John. Gaius responds with generosity and hospitality, while Diotrephes responds with arrogance and opposition. John commends Gaius for walking in the truth and condemns Diotrephes for walking in error. Gaius is praised for applying and living out the teachings of the apostles, whereas Diotrephes, a selfish church leader, refuses to help these godly teachers, slanders John, and opposes those who disagree with him. This book demonstrates that pettiness can divide Christians if they are not living by God's Word. John encourages members of God's church to practice love and discernment in truth to avoid the dangers of false teaching and division. He assures Gaius of his prayers for his health and expresses joy over Gaius's persistent walk in the truth and his hospitality towards traveling ministers. By supporting these ministers, Gaius becomes a fellow worker of the truth. Diotrephes, on the other hand, rejects John's apostolic authority, refuses to receive traveling teachers, and excommunicates loyal members who do not follow his lead. John plans to address Diotrephes' actions upon his arrival. The epistle concludes with a personal farewell greeting, emphasizing the peace of Jesus Christ amidst contention and disunity in the church.

III John is written to a Christian named Gaius, commending him for his hospitality towards visiting teachers and encouraging him to continue this practice. The letter also indirectly rebukes Diotrephes for refusing to welcome these teachers and for hindering others from doing so. Additionally, III John presents Demetrius as a positive example in these matters. The letter encourages a positive approach towards receiving true servants of God, contrasting with the negative approach of not receiving false teachers mentioned in II John.