John Chrysostom, on 1Cor 9:27

"But I buffet my body, and bring it into bondage lest by any means, after that I have preached to others, I myself should be rejected."

Here he implies that they are subject to the lust of the belly and give up the reins to it, and under a pretence of perfection fulfil their own greediness; a thought which before also he was travailing to express, when he said, "meats for the belly, and the belly for meats." For since both fornication is caused by luxury, and it also brought forth idolatry, he naturally oftentimes inveighs against this disease; and pointing out how great things he suffered for the Gospel, he sets this also down among them. "As I went," saith he, "beyond the commands, and this when it was no light matter for me:" ("for we endure all things," it is said,) "so also here I submit to much labor in order to live soberly. Stubborn as appetite is and the tyranny of the belly, nevertheless I bridle it and give not myself up to the passion, but endure all labor not to be drawn aside by it."

"For do not, I pray you, suppose that by taking things easily I arrive at this desirable result. For it is a race and a manifold struggle, and a tyrannical nature continually rising up against me and seeking to free itself. But I bear not with it but keep it down, and bring it into subjection with many struggles." Now this he saith that none may despairingly withdraw from the conflicts in behalf of virtue because the undertaking is laborious. Wherefore he saith, "I buffet and bring into bondage." He said not, "I kill:" nor, "I punish" for the flesh is not to be hated, but, "I buffet and bring into bondage;" which is the part of a master not of an enemy, of a teacher not of a foe, of a gymnastic master not of an adversary.

"Lest by any means, having preached to others, I myself should be a rejected."

Now if Paul feared this who had taught so many, and feared it after his preaching and becoming an angel and undertaking the leadership of the whole world; what can we say?

For, "think not," saith he, "because ye have believed, that this is sufficient for your salvation: since if to me neither preaching nor teaching nor bringing over innumerable persons, is enough for salvation unless I exhibit my own conduct also unblameable, much less to you."