Jamieson, Fausset and Brown on 3 John 1:6

6. borne witness of thy charity before the church--to stimulate others by the good example. The brethren so entertained by Gaius were missionary evangelists (3Jo 7); and, probably, in the course of narrating their missionary labors for the edification of the Church where John then was, incidentally mentioned the loving hospitality shown them by Gaius.

bring forward on their journey--"If thou (continue to) forward on their journey" by giving them provisions for the way.

after a godly sort--Greek, "in a manner worthy of God," whose ambassadors they are, and whose servant thou art. He who honors God's missionary servants (3Jo 7), honors God.