1:9-12 Both the heart and mouth must be watched. The temper and spirit of Diotrephes was full of pride and ambition. It is bad not to do good ourselves; but it is worse to hinder those who would do good. Those cautions and counsels are most likely to be accepted, which are seasoned with love. Follow that which is good, for he that doeth good, as delighting therein, is born of God. Evil-workers vainly pretend or boast acquaintance with God. Let us not follow that which is proud, selfish, and of bad design, though the example may be given by persons of rank and power; but let us be followers of God, and walk in love, after the example of our Lord.

12. of all men—who have had opportunity of knowing his character.

of the truth itself—The Gospel standard of truth bears witness to him that he walks conformably to it, in acts of real love, hospitality to the brethren (in contrast to Diotrephes), &c. Compare Joh 3:21 "He that doeth truth cometh to the light, that his deeds may be made manifest that they are wrought in God."

we also—besides the testimony of "all men," and "of the truth itself."

ye know—The oldest manuscripts read, "thou knowest."