3 John 1:12

12 The body of the letter closes with a commendation of Demetrius, the bearer of the letter, as a faithful Christian. Such commendation by name, like the naming of the addressee of the letter, was necessary to ensure that the letter was neither suppressed nor misused by those who, like Diotrephes, would disrupt the unity of the congregation (v. 9). Demetrius may have been a traveling teacher himself; if so, John’s letter would encourage Gaius to show hospitality.