Expositor's Bible Commentary Commentary 1 Corinthians 9:18

"What then is my reward? That, when I preach the gospel, I may make the gospel without charge, so as not to use to the full my right in the gospel." — 1 Corinthians 9:18 (ASV)

It is true that there is reward or pay in preaching, but only if done without pay. Paul states the alternatives. If he preaches freely, voluntarily, he has a reward; if for pay, he is merely fulfilling the commission entrusted to him (Acts 26:16). His reward is the boasting he can make before them that he is preaching to them without charge and not making use of his rights as a gospel minister. Paul wants to prove to the Corinthians the genuineness of his ministry.