1 Corinthians 9:18-19

18So what kind of pay do I receive? It is this: I do not take any money from people when I tell them God's good news. I do not use all the authority that I could use when I tell God's good news to people.

19Yes, I am a free man. I am not anybody's slave. But I choose to serve everybody like a slave. I do that so that I can help many more people to believe in Christ.