1 Corinthians 9:13-17

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 have not written these things so that it will be done so in my case; for it would be better for me to die than that. No one shall make my boast an empty one!

For if I preach the gospel, I have nothing to boast about, for I am under compulsion; for woe to 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 been entrusted with a commission nonetheless.