2 Corinthians 11:7

Or did I commit a sin in abasing myself that ye might be exalted, because I preached to you the gospel of God for nought? [A second accusation which his enemies never wearied in presenting was that he had preached the gospel in Corinth without charge. They had said that he did this because he knew that he was not an apostle, and so was hindered by his conscience from taking the wages of an apostle--see 1 Corinthians 9:1-15 and notes. As Paul has already refuted this charge, he does not repeat the refutation; he merely asks them if he had committed a sin in so doing.]