1 Corinthians 9:14-17

Even so did the Lord ordain that they that proclaim the gospel should live of the gospel. But I have used none of these things: and I write not these things that it may be so done in my case; for it were good for me rather to die, than that any man should make my glorying void. For if I preach the gospel, I have nothing to glory of; for necessity is laid upon me; for woe is unto me, if I preach not the gospel. For if I do this of mine own will, I have a reward: but if not of mine own will, I have a stewardship intrusted to me.