Charles Ellicott Commentary 1 Corinthians 9:17

"For if I do this of mine own will, I have a reward: but if not of mine own will, I have a stewardship intrusted to me." — 1 Corinthians 9:17 (ASV)

For if I do this thing willingly, I have a reward. The previous words, Indeed, woe is unto me if I preach not the gospel, are a parenthesis. Now the writer proves the truth of his assertion: that the necessity of preaching the gospel deprives the mere act itself of any grounds for boasting, by showing that if there were no necessity, there would be a ground for boasting.

The argument is this: Suppose it were otherwise, and that there is no such necessity; then, by voluntarily undertaking it, I have a reward. Undertaking it of my own free will would entitle me to a reward. But if (as is the case) it is not of my own free will but of necessity, then I am merely a steward—a slave doing his duty (1 Corinthians 4:1; Luke 17:7–10).

A dispensation of the gospel is committed unto me. Better, I am entrusted with a stewardship.