Matthew 6:16-18

16 Moreover when ye fast, be not, as the hypocrites, of a sad countenance: for they disfigure their faces,
that they may appear unto men to fast. Verily I say unto you, They have their reward.

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.