Matthew 6:16-19

Moreover when ye fast, be not, as the hypocrites, of a sad countenance: for they disfigure their faces, that they may be seen of men to fast. Verily I say unto you, They have received their reward. But thou, when thou fastest, anoint thy head, and wash thy face; that thou be not seen of men to fast, but of thy Father who is in secret: and thy Father, who seeth in secret, shall recompense thee. Lay not up for yourselves treasures upon the earth, where moth and rust consume, and where thieves break through and steal