1 Corinthians 9:25-27

Haweis(i) 25 And every one who contendeth [in the games] is temperate in all things: they indeed therefore do it that they may receive a corruptible crown, but we an incorruptible. 26 I therefore so run not as uncertainly; so do I exercise with my fists, not as striking the air: 27 but I beat down my body, and bring it into subjection, that I may not by any means, after having preached to others, myself become reprobate.