diligent. Same as "forward", 2 Corinthians 8:17.
upon. through. No preposition.
confidence. Greek. pepoithesis. App-150.
I have. Supply the ellipsis by "he has". This was the reason of his diligence.
Related Commentaries of 2 Corinthians 8:22
2 Corinthians 8:22
22 And we have sent with them our brother, whom we have oftentimes proved diligent in many things, but now much more diligent, upon the great confidence which I have in you.