What is my reward then? - What is the source of my reward? or what is there in my conduct that will show that I am entitled to reward What is there that will demonstrate that my heart is in the work of the ministry; that I am free and voluntary, and that I am not urged by mere necessity? Though I have been called by miracle, and though necessity is laid upon me, so that I cannot but preach the gospel, yet how shall I so do it as to make it proper for God to reward me as a voluntary agent? Paul immediately states the circumstance that showed that he was entitled to the reward, and that was, that he denied himself, and was willing to forego his lawful enjoyments, and even his rights, that he might make the gospel without charge.

I may make the gospel of Christ without charge - Without expense to those who hear it. I will support myself by my own labor, and will thus show that I am not urged to preaching by mere "necessity," but that I love it. Observe here