William Burkitt on 1 Corinthians 9:26

That is, "I run this race of Christianity myself, which I advise you unto. But my care is to run sure, not at uncertainties; to make sure of the crown at the end of the race, and I do not only run, but fight; I oppose whatever opposeth me."

Here observe, The apostle changes the metaphor from that of running to the other game of cuffing; and says he did not fight like one that beats the air, but never hurts the adversary; no, he fought in good earnest with all his spiritual enemies, the flesh, the world, and the devil. It is not every running that will gain the prize, nor every fighting that will obtain the victory; but it must be a running with all perseverance, and a fighting with our utmost power, that will bring us to heaven and eternal happiness.