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. But thou, when thou fastest, anoint thine head, and wash thy face; 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.
When we fast, we are to do it in secret, giving no outward appearance of it. We are not to deliberately attempt to show that we are fasting. The hypocrites disfigured their faces when they fasted in order to appear gaunt, haggard, and doleful. Jesus said it is ridiculous to attempt to appear holy, as we are to just be holy.