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. [He was commanded to preach the gospel. He could not glory therefore in doing it, for he did not do it of his own free will or choice (however cheerfully and willingly he might do it), but because it was a stewardship which he was obliged to discharge (Luke 17:10). Had he been free to preach the gospel or not, he might have gloried in preaching it. But as it was, he had to seek glory elsewhere.]