'Fast' in the Bible

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.

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.

Then come to him the disciples of John, saying, Why do we and the Pharisees fast oft, but thy disciples fast not?

And Jesus said unto them, Can the sons of the bridechamber mourn, as long as the bridegroom is with them? but the days will come, when the bridegroom shall be taken away from them, and then will they fast.