Which have borne witness of thy charity before the church - It would seem that they had returned to John, and borne honorable testimony to the love manifested to them by Gaius. Before what church they had borne this testimony is unknown. Perhaps it was the church in Ephesus.
Whom if thou bring forward on their journey - οὕς προπέμψας hous propempsas. “Whom bringing forward, or having brought forward.” The word refers to aid rendered to them in their journey, in facilitating their travels, either by personally accompanying them, by furnishing them the means of prosecuting their journey, or by hospitably entertaining them. Gaius probably aided them in every way in which it was practicable. It has been made a question whether this refer, to the fact that he had thus aided them in some visit which they had made to the church where Gaius was, or to a visit which they purposed to make. The Greek would seem to favor the latter construction, and yet it would appear from the Epistle, that the “brethren and strangers” actually had been with him that they had been rejected by the church through the influence of Diotrephes, and had been thrown upon the hospitality of Gaius, and that they had returned, and had borne honorable testimony to his hospitality. These views can be reconciled by supposing, as Lucke does, that having been once on their travels, and having shared the hospitality of Gaius, they were purposing to visit that region again, and that John, praising him for his former hospitality, commends them again to him, stating the reason 3 John 1:9-10 why he did not, in accordance with the usual custom, recommend them to the care of the church. They had now gone out 3 John 1:7 on the same errand upon which they had formerly gone, and they had now equal claims to the hospitality of the friends of religion.
After a godly sort - Margin, as in Greek, “worthy of God.” The meaning is, As becomes those who serve God; or as becomes those who are professors of his religion.
Thou shalt do well - You will do what religion requires in these circumstances.