1 Corinthians 9:13-18

Do you not know that those who perform sacred services eat the food of the temple, and those who attend regularly to the altar have their share from the altar? So also the Lord directed those who proclaim the gospel to get their living from the gospel. But I have used none of these things. And I am not writing these things so that it will be done so in my case; for it would be better for me to die than have any man make my boast an empty one. For if I preach the gospel, I have nothing to boast of, for I am under compulsion; for woe is me if I do not preach the gospel. For if I do this voluntarily, I have a reward; but if against my will, I have a stewardship entrusted to me. What then is my reward? That, when I preach the gospel, I may offer the gospel without charge, so as not to make full use of my right in the gospel.