Matthew 6:16-18

“And when you fast, do not put on a sad face as the hypocrites do. They neglect their appearance so that everyone will see that they are fasting. I assure you, they have already been paid in full. When you go without food, wash your face and comb your hair, so that others cannot know that you are fasting — only your Father, who is unseen, will know. And your Father, who sees what you do in private, will reward you.