1Cor 9:15-18

15But I have made no use of any of these rights, nor am I writing this so that they may be applied in my case. Indeed, I would rather die than that—no one will deprive me of my ground for boasting!16If I proclaim the gospel, this gives me no ground for boasting, for an obligation is laid on me, and woe to me if I do not proclaim the gospel!17For if I do this of my own will, I have a reward; but if not of my own will, I am entrusted with a commission.18What then is my reward? Just this: that in my proclamation I may make the gospel free of charge, so as not to make full use of my rights in the gospel.