1 Corinthians 9:16-17

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.