Matthew 6:16-18

16And when ye fast, be not as the hypocrites, downcast in countenance; for they disfigure their faces, so that they may appear fasting to men: verily I say unto you, They have their reward.

17But thou, [when] fasting, anoint thy head and wash thy face,

18so that thou mayest not appear fasting unto men, but to thy Father who is in secret; and thy Father who sees in secret shall render [it] to thee.