1:5 Dear friend, 1 you demonstrate faithfulness 2 by whatever you do for the brothers (even though they are strangers).
1 tn The author has already described Gaius as “dear friend” or “beloved” (τῷ ἀγαπητῷ, tw agaphtw) in v. 1; he will address Gaius in the same way in vv. 5 and 11 (᾿Αγαπητέ, Agaphte). This is a term of endearment and personal warmth, much as it is when used by the author as an address in 1 John 2:7.
2 tn BDAG 821 s.v. πιστός 1.b offers the translation “act loyally” for this context, a usage which is not common but does fit well here. Since the author is going to ask Gaius for additional help for these missionaries in the following verse, he begins here by commending Gaius for all that he has already done in this regard.
sn When the author tells Gaius “you demonstrate faithfulness by whatever you do” he is commending him for his faithful service to the traveling missionaries (the brothers). Gaius has assisted them, and they have now returned with a report of this to the author (3 John 3).
3 sn The exhortation do not imitate what is bad but what is good is clearly a reference to Diotrephes’ evil behavior. The author exhorts Gaius (whom he wishes to continue assisting the missionaries) not to follow the negative example of Diotrephes, but to do what is right. Implicitly there may be a contrast between the bad behavior of Diotrephes and the good reputation of Demetrius (mentioned in the following verse); but it seems more likely that Demetrius is himself one of the traveling missionaries (perhaps their leader), rather than the leader of a local congregation who, unlike Diotrephes, has supported the missionaries himself.
4 sn The statement The one who does what is bad has not seen God is asyndetic; its abrupt introduction adds emphasis. The statement reiterates the common Johannine theme of behavior as an indication of genuine faith, found in 1 John in 3:6, 10; 4:7, 20; and in the Gospel of John in 3:17-21. By implication, the genuineness of Diotrephes’ faith is called into question, because he has obviously done what is bad (v. 11b; cf. vv. 9-10). In John’s terminology it is clear that the phrase has not seen God is equivalent to “is not a genuine Christian” (see John 3:17-21 and 1 John 3:6, 10; 4:7, 20).