1 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.
2 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).
3 tn The third-class condition (ἐὰν ἔλθω, ean elqw) seems to be used by the author to indicate real uncertainty on his part as to whether he will visit Diotrephes’ church or not.
4 sn Because Diotrephes did not recognize the authority of the author, the author will expose his behavior for what it is (call attention to the deeds he is doing) if he comes for a visit. These are the charges the author will make against Diotrephes before the church: (1) Diotrephes is engaged in spreading unjustified charges against the author with evil words; (2) Diotrephes refuses to welcome the brothers (the traveling missionaries) himself; (3) Diotrephes hinders the others in the church who wish to help the missionaries; and (4) Diotrephes expels from the church (throws them out) people who aid the missionaries. (Diotrephes himself may not have had supreme authority in the local church to expel these people, but may have been responsible for instigating collective action against them.)