'Fast' in the Bible

'And when ye may fast, be ye not as the hypocrites, of sour countenances, for they disfigure their faces, that they may appear to men fasting; verily I say to you, that they have their reward.

Then come to him do the disciples of John, saying, 'Wherefore do we and the Pharisees fast much, and thy disciples fast not?'

And Jesus said to them, 'Can the sons of the bride-chamber mourn, so long as the bridegroom is with them? but days shall come when the bridegroom may be taken from them, and then they shall fast.