1 Corinthians 9:16-18

For if I [merely] preach the gospel, I have nothing to boast about, for I am compelled [that is, absolutely obligated to do it]. Woe to me if I do not preach the good news [of salvation]! For if I do this work of my own free will, then I have a reward; but if it is not of my will [but by God’s choosing], I have been entrusted with a [sacred] stewardship. What then is my reward? [Just this:] that, when I preach the gospel, I may offer the gospel without charge [to everyone], so as not to take advantage of my rights [as a preacher and apostle] in [preaching] the gospel.