1 Corinthians 9:25-27 (KJV)

²⁵And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible.

²⁶I therefore so run, not as uncertainly; so fight I, not as one that beateth the air:

²⁷But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.