16Yet when I preach the gospel, I have no reason to boast, because I am obligated to preach. Woe to me if I do not preach the gospel!
17If my preaching is voluntary, I have a reward. But if it is not voluntary, I am still entrusted with a responsibility.
18What then is my reward? That in preaching the gospel I may offer it free of charge, and so not use up my rights in preaching it.
— 1 Corinthians 9:16-18