'Fasting' in the Bible

And the disciples of John and the Pharisees were fasting; and they come and say to him, Why do the disciples of John and the disciples of the Pharisees fast, but thy disciples fast not?

and if I should dismiss them to their home fasting, they will faint on the way; for some of them are come from far.

And he said to them, This kind can go out by nothing but by prayer and fasting.