Matthew 6:16-18
16 “And whenever you fast, do not look dismal, like the hypocrites, for they disfigure their faces so as to show others that they are fasting. Truly I tell you, they have received their reward. 17 But when you fast, put oil on your head and wash your face, 18 so that your fasting may be seen not by others but by your Father who is in secret; and your Father who sees in secret will reward you.