1 Corinthians 9:24-27

Know ye not that they that run in a race run all, but one receiveth the prize? Even so run; that ye may attain. And every man that striveth in the games exerciseth self-control in all things. Now they do it to receive a corruptible crown; but we an incorruptible. I therefore so run, as not uncertainly; so fight I, as not beating the air: 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.