1 Corinthians 9:27

but I buffet my body, and bring it into bondage [The body, being, as it is in part, the seat and organ of sin, has become the Biblical term to express our whole sinful nature (Romans 8:13). Paul found in this old sinful man with its corrupt affections an ever-present antagonist. He ran no uncertain race with his body, realizing that God would give him the victory if he ran his best. He fought no uncertain fight with it, but so smote it as to bring it into subjection. By smiting he does not mean literal flagellation, self-torture or even fasting, but he means that he subdues his nature by denying its lusts (Colossians 3:5), and that he employed his body in noble labor, with all self-denial and self-sacrifice, for the good of others-- 2 Corinthians 6:4-5; 2 Corinthians 11:23-33]: lest by any means, after that I have preached to others, I myself should be rejected. [The word translated "preached" means literally to "proclaim as a herald." It is the word used in the New Testament to describe the preaching of the gospel, and so the reader is at liberty to follow the English version, and drop the metaphor of which Paul has been making use. If he does this, then Paul tells him literally that even he had fears that he might fall from grace, and therefore daily worked out his own salvation with fear and trembling (Philippians 2:12) But if "preached" be translated "acted or proclaimed as herald," then Paul conveys to us the same thought metaphorically. It was the duty of the herald to move up and down the lists and proclaim aloud the laws of the contests, the names of the contestants, victors, etc. These laws said in brief that no slave, thief, or man of bad morals, would be admitted as a contestant. Thus construed, Paul expresses a fear lest having laid down the gospel terms of salvation to others, he himself should be rejected for having failed to comply with the very rules which his own mouth had proclaimed (Luke 19:22; Romans 2:1-3). While it was not customary for heralds to be contestants, such a thing was not impossible, for the emperor Nero once played both parts. He was combatant, victor, and herald to proclaim his own triumphs. The metaphors of Paul, like the parables of Jesus, caused the scenes of daily life to suggest great spiritual truths to those who beheld them.]