The writer now passes on to his next topic, the recommendation of Demetrius (verse 12), marking the transition by verse 11. In this verse he warns against doing evil, taking his cue from the bad behavior of Diotrephes. And he exhorts Gaius to do good, thus leading over to Demetrius, “who has testimony … from the truth itself.”

This Demetrius is not to be identified with the one of Acts 19.24, 38; nothing else is known of him. He probably was one of the traveling preachers and as such may have been the bearer of the present letter.

Do not imitate evil, or ‘do not follow bad examples,’ ‘do not act/be like people who are doing evil,’ ‘do not follow the deeds of bad men.’

To do good and to do evil, or ‘to do what is good’ and ‘to do what is evil.’

For is of God, compare comments on “is … of the Father” in 1 John 2.16.

Has not seen God: the verse does not mean to imply the reverse, namely, that he who does good can see God. John nowhere says in his writings that men in the present age can actually have a direct vision of God (compare comments on 1 John 4.12). Consequently the idiom must be taken here as expressing not the actual vision of God but intimate relationship and fellowship with God. Therefore some versions say ‘has not known (or does not know) God.’ The verb is in the perfect tense, indicating an event in the past effecting the present.

Quoted with permission from Haas, C., de Jonge, M. and Swellengrebel, J.L. A Handbook on The Third Letter of John. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .