For though I preach the gospel, I have nothing to glory of: for necessity is laid upon me; yea, woe is unto me, if I preach not the gospel!

People's New Testament

9:16 For though I preach the gospel, I have nothing to glory of. He preached because he was Christ's servant. He was therefore under necessity, as a servant. Nay, woe was upon him if he obeyed not. In this, then, he had no right to boast. But if he refused a support from the churches when he had liberty to receive it, that might make a ground of boasting.

Jamieson-Fausset-Brown Bible Commentary

16. though I preach . I have nothing to glory of-that is, If I preach the Gospel, and do so not gratuitously, I have no matter for "glorying." For the "necessity" that is laid on me to preach (compare Jer 20:9, and the case of Jonah) does away with ground for "glorying." The sole ground for the latter that I have, is my preaching without charge (1Co 9:18): since there is no necessity laid on me as to the latter, it is my voluntary act for the Gospel's sake.

Matthew Henry's Concise Commentary

9:15-23 It is the glory of a minister to deny himself, that he may serve Christ and save souls. But when a minister gives up his right for the sake of the gospel, he does more than his charge and office demands. By preaching the gospel, freely, the apostle showed that he acted from principles of zeal and love, and thus enjoyed much comfort and hope in his soul. And though he looked on the ceremonial law as a yoke taken off by Christ, yet he submitted to it, that he might work upon the Jews, do away their prejudices, prevail with them to hear the gospel, and win them over to Christ. Though he would transgress no laws of Christ, to please any man, yet he would accommodate himself to all men, where he might do it lawfully, to gain some. Doing good was the study and business of his life; and, that he might reach this end, he did not stand on privileges. We must carefully watch against extremes, and against relying on any thing but trust in Christ alone. We must not allow errors or faults, so as to hurt others, or disgrace the gospel.