John’s second and third letters related to specific situations in churches with whom he was familiar. John was concerned for his readers to grasp the significance of Jesus’ coming in the flesh and the necessity of responding to God’s love in Christ by loving the brethren. When many began to abandon these fundamental Christian doctrines, John was inspired to write messages of warning to the faithful—lest more be led astray by falsehood. Though John had particular issues to address in 2-3 John, the logic of his instructions displayed a mindset grounded in God’s redemptive work in the history of Israel and in Christ.
Third John was a personal letter. He was writing to Gaius, whom he said that he loved in the truth (3 John 1). Gaius’ firm commitment to the truth—especially his hospitality to traveling teachers—encouraged John’s heart (3 John 5-8). In 3 John 5, John commended Gaius for his hospitality, echoing commands for Israel to welcome strangers. Abraham’s hospitality to the three visitors, those who prophesied that Abraham and Sarah would conceive a child even in their old age (Gen 18:1-15), established a tradition of hospitality in Israel. Moses commanded Israel to leave portions for the stranger dwelling among them (Deut 24:14-15, 19-21). Isaiah prophesied that even the temple, the sacred structure of Israel, was to be a place of welcome for the foreigner (Isa 56:1-8).
In 3 John 9-10, John condemned Diotrophes because he did not show hospitality to any of John’s missionary companions. Diotrophes not only refused to offer hospitality to traveling Christians, but even excommunicated any who attempted to come to the aid of those traveling to spread the word of Christ (3 John 9-11). All of this was to set the stage for John’s request that Gaius provide hospitality to Demetrius—one who had a good testimony and lived consistent with the message of the truth (3 John 12).