1 Corinthians 9:16-19

9:16 For if I preach the gospel, I have no reason for boasting, because I am compelled to do this. Woe to me if I do not preach the gospel! 9:17 For if I do this voluntarily, I have a reward. But if I do it unwillingly, I am entrusted with a responsibility. 9:18 What then is my reward? That when I preach the gospel I may offer the gospel free of charge, and so not make full use of my rights in the gospel.

9:19 For since I am free from all I can make myself a slave to all, in order to gain even more people.