Follow not that which is evil,— Imitate not, &c. As Diotrephes seems to have been pastor of the church where Gaius lived, and a zealous, conceited, Judaizing Christian, it is not unlikely but he made boasting pretensions to greater knowledge of God and of the Gospel than St. John had; and lest such glorying should recommend his bad example, and make him pass for a person of high reputation, St. John cautions Gaius against following his example; and recommends to him rather the imitation of such plain honest Christians as kindly received those whotravelled about to preach the gospel to the Gentiles. It is very likely that they boasted not of their own knowledge, but behaved well; and that was a much better proof of their understanding the nature of God, and of the gospel of Christ, than any pretensions to uncommon knowledge, without a suitable temper and conduct.
Related Commentaries of 3 John 1:11
3 John 1:11
11 Beloved, follow not that which is evil, but that which is good. He that doeth good is of God: but he that doeth evil hath not seen God.