And we have sent with them our brother - Who this was is wholly unknown; and conjecture is useless. Some have supposed that it was Apollos, others Silas, others Timothy. But there are no means of ascertaining who it was; nor is it material. It was some one in whom Paul had entire confidence.
Whom we have oftentimes proved diligent - Of whom we have evidence that he has been faithful. It is evident, therefore, that he had been the companion and fellow-laborer of Paul.
But now much more diligent ... - Who will now prove himself much more diligent than ever before.
Upon the confidence ... - Margin, “he hath.” The margin is doubtless the more correct reading here. The idea is, that this brother had great confidence in the Corinthians that they would give liberally, and that he would, therefore, evince special diligence in the business.