2 Corinthians 8:22

And we have sent with them our brother, whom we have many times proved earnest in many things, but now much more earnest, by reason of the great confidence which he hath in you. [As to this third party, Alford well says, "Every possible person has been guessed." There is no means of determining who it was. Paul's words show that he had been often used by the apostle because of his earnestness, and that he was employed in this work because he evidently knew and had great confidence in the Corinthians.]