A.T. Robertson Commentary 3 John 1:11

"Beloved, imitate not that which is evil, but that which is good. He that doeth good is of God: he that doeth evil hath not seen God." — 3 John 1:11 (ASV)

Imitate not (μη μιμου). Present middle imperative in prohibition (do not have the habit of imitating) of μιμεομα (from μιμος, actor, mimic), old word, in N.T. only here, 2 Thessalonians 3:7,9; Hebrews 13:7.

That which is evil (το κακον). "The bad," as in Ro 12:21 (neuter singular abstract).

But that which is good (αλλα το αγαθον). "But the good." As in Ro 12:21 again. Probably by the contrast between Diotrephes and Demetrius.

He that doeth good (ο αγαθοποιων). Articular present active participle of αγαθοποιεω, late and rare verb, in contrast with ο κακοποιων (old and common verb) as in Mr 3:4; Luke 6:9; 1 Peter 3:17.

Is of God (εκ του θεου εστιν). As in 1 John 3:9f.

Hath not seen God (ουχ εωρακεν τον θεον). As in 1 John 3:6. He does not say εκ του διαβολου as Jesus does in Joh 8:44, but he means it.