1 Corinthians 9:16-17

NSB(i) 16 Though I preach the good news I do not brag about it. Preaching the good news is my duty (obligation) and I must do it! It would be terrible if I did not preach the good news! 17 For if I do this thing willingly, I have a reward. But if I do it against my will, I am just performing the trust of the good news committed to me.