Matthew 6:16-18 - The Sermon On The Mount: How To Fast
16 And when ye fast, be not as the hypocrites, affecting a gloomy look: for they disfigure their visages, that they may make a shew of fasting to men. Verily I say unto you, That they have their reward. 17 But when thou keepest a fast, anoint thine head, and wash thy face; 18 that thou mayest not make a shew of fasting to men, but to thy Father who is in secret: and thy Father who seeth in secret shall reward thee openly.