Matthew 6:16-18

“When you fast, do not look sullen like the hypocrites, for they make their faces unattractive so that people will see them fasting. I tell you the truth, they have their reward. When you fast, put oil on your head and wash your face, so that it will not be obvious to others when you are fasting, but only to your Father who is in secret. And your Father, who sees in secret, will reward you.