3 John 1:12
Demetrius hath good report of all men, and of the truth itself: yea, and we also bear record; and ye know that our record is true. Demetrius hath good report of all men, and of the truth itself: yea, and we also bear record; and ye know that our record is true.
The commendation belongs to a personal letter addressed to Gaius concerning the duty of extending hospitality and a kind reception to brethren who were preaching the gospel to the Gentiles. Within that setting Demetrius is singled out for praise as one worthy of such welcome and support. His character is attested as having a good report from all men and from the truth itself. To that double testimony is added John's own personal witness, declared to be true.
The praise stands in deliberate contrast to Diotrephes, who loved to have the preeminence among the church. Diotrephes did not receive John, refused the traveling brethren himself, forbade those who were willing to receive them, and cast such supporters out of the church. Against that evil course Demetrius is set forth as the good example to be followed rather than evil. To follow him is to follow one approved by men, vindicated by the truth, and confirmed by apostolic record.