So that you may not appear to men to be fasting, but to your Father who is in secret; and your Father who sees in secret will repay you.
This indicates that our fasting, like our giving of alms and praying, must be done in secret, not before men. The Father sees in secret, and He will repay us.
Making a public display before men will never help us grow in life. If you want to grow and be healthy in the spiritual life, you must slay the self in the doing of righteous deeds. No matter what kind of righteous deeds we do—giving material things to the saints, praying, fasting, doing something to please God—we must try our best to do them in secret. If your righteous deeds are in secret, you may be assured that you are growing in life and are healthy.