Matthew 6:16-18

“And whenever you are fasting, do not look gloomy like the hypocrites, for they put on a sad and dismal face [like actors, discoloring their faces with ashes or dirt] so that their fasting may be seen by men. I assure you and most solemnly say to you, they [already]have their reward in full. [Is 58:5] But when you fast, put oil on your head [as you normally would to groom your hair] and wash your face so that your fasting will not be noticed by people, but by your Father who is in secret; and your Father who sees [what is done]in secret will reward you.