3 John 1:1
1 The elder unto the wellbeloved Gaius, whom I love ina the truth.
It is probable that the Gaius to whom this letter was sent is the Gaius of Corinth 1 Corinthians 1:14). Its subject is hospitality as revealing love, and the apostle uttered a warning against schism. As in the letter to the "elect lady," the keynote is Truth. In that John warned against false hospitality. Here he commands true hospitality. He charged Gaius to set forth certain evangelists "worthily of God." This is a remarkable phrase, and probably means, first, that Gaius was to see in these men the messengers of God, and, second, that he was to act as a child of God.
In striking contrast to Gaius stands Diotrephes. The whole truth about him is revealed in the words "Diotrephes, who loveth to have the preeminence." That is the essential violation of love. His heterodoxy was of spirit and temper rather than of intellect.
Another character introduced in the letter is Demetrius. In all probability he was the bearer of the letter, and John quoted him in direct contrast to Diotrephes.
The central statement of the epistle is in the words, "He that doeth good is of God: he that doeth evil hath not seen God." Doing good is to be interpreted by the subject of the letter, namely, hospitality. Those who thus act in love do so because they are of God, that is, related to Him in the fellowship of life. Such were Gaius and Demetrius. Those who act selfishly do so because they have no fellowship with God. The writer closes with words anticipatory of a meeting, and a message of peace.