1 Corinthians 9:16-19

16For though I preach the gospel, I have nothing to glory of: for necessity is laid upon me; yea, woe is unto me, if I preach not the gospel! 17For if I do this thing willingly, I have a reward: but if against my will, a dispensation of the gospel is committed unto me. 18What is my reward then? Verily that, when I preach the gospel, I may make the gospel of Christ without charge, that I abuse not my authority in the gospel.

19For though I be free from all men, yet have I made myself servant unto all, that I might gain the more.