Paul’s subsequent explanation (of why his work in proclaiming the gospel is no ground for boasting
) is somewhat vague. The ESV attempts to clarify the meaning of this verse through the phrase of my own will.
This, however, is not an obvious translation of the original, which simply means willingly.
Moreover, the rest of Scripture teaches that no one can become a preacher out of his own will. All true preachers are sent by God (Romans 10:15).
Paul speaks of two ways of proclaiming the gospel: willingly
and unwillingly.
His point might be that even if he were unwilling to proclaim the gospel, it would make no difference. He would still be entrusted with a stewardship.
17 For if I do this of my own will, I have a reward, but if not of my own will, I am still entrusted with a stewardship.