1 Corinthians 9:2 - Ellicott's Commentary On The Whole Bible

If I be not an apostle unto others. — The allusion here is probably to some who may have arrived at Corinth subsequent to St. Paul’s departure, and who, not recognising his Apostleship in relation to themselves, stirred up some of the Corinthians to repudiate it also. So the Apostle says, “Even if I am not an Apostle to these others, I am, at all events, to you; for you are yourselves the very proof and witness — the seal affixed to my appointment to the Apostolate.” The repetition of the words “in the Lord” in both these verses expresses the strong conviction, which is characteristic of the Apostle, that the source of all power and of all success is Christ Himself.