Matthew 6:16-18

16 “Moreover when you fast, don't be like the hypocrites, with sad faces. For they disfigure their faces, that they may be seen by men to be fasting. Most assuredly I tell you, they have received their reward.  17 But you, when you fast, anoint your head, and wash your face;  18 so that you are not seen by men to be fasting, but by your Father who is in secret, and your Father, who sees in secret, will reward you.