1 Corinthians 9:14-17

In the same way, the Lord has commanded that those who tell the Good News should get their living from this work. But I have not used any of these rights. And I am not writing this now to get anything from you. I would rather die than to have my reason for bragging taken away. Telling the Good News does not give me any reason for bragging. Telling the Good News is my duty—something I must do. And how terrible it will be for me if I do not tell the Good News. If I preach because it is my own choice, I have a reward. But if I preach and it is not my choice to do so, I am only doing the duty that was given to me.