Matthew 6:18 in the World English Bible
so that you are not seen by men to be fasting, but by your Father who is in secret; and your Father, who sees in secret, will reward you.
Context
17 But thou, when thou fastest, anoint thine head, and wash thy face;
18 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.
19 Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal: