Matthew 6:16-18

16 "When you give up eating, don't put on a sad face like the hypocrites. They make their faces look sad to show people they are giving up eating. I tell you the truth, those hypocrites already have their full reward.

17 So when you give up eating, comb your hair and wash your face.

18 Then people will not know that you are giving up eating, but your Father, whom you cannot see, will see you. Your Father sees what is done in secret, and he will reward you.