1 Corinthians 9:16-19

16For though I preach the gospel, I have nothing to boast of: for necessity is laid upon me; and, woe is to 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 to me. 18What is my reward then? Verily that, when I preach the gospel, I may make the gospel of Christ without charge, that I may not abuse my right in the gospel.

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