1 Corinthians 9:15-19

But I have not used any of these rights. And I am not writing this in the hope that you will do such things for me, for I would rather die than allow anyone to deprive me of this boast. For when I preach the gospel, I cannot boast, since I am compelled to preach. Woe to me if I do not preach the gospel! If I preach voluntarily, I have a reward; if not voluntarily, I am simply discharging the trust committed to me. What then is my reward? Just this: that in preaching the gospel I may offer it free of charge, and so not make full use of my rights as a preacher of the gospel. Though I am free and belong to no one, I have made myself a slave to everyone, to win as many as possible.