So that it will not be obvious to others that you are fasting, but only to your Father, who is unseen; and your Father, who sees what is done in secret, will reward you. (NIV)
So that your fasting may not be noticed by men but by your Father, Who sees in secret; and your Father, Who sees in secret, will reward you in the open. (AMP)
That thou appear not unto men to fast, but unto thy Father which is in secret: and thy Father, which seeth in secret, shall reward thee openly. (KJV)