'Fast' in the Bible

“Whenever you fast, do not put on a gloomy face as the hypocrites do, for they neglect their appearance so that they will be noticed by men when they are fasting. Truly I say to you, they have their reward in full.

But you, when you fast, anoint your head and wash your face

Then the disciples of John *came to Him, asking, “Why do we and the Pharisees fast, but Your disciples do not fast?”

And Jesus said to them, “The attendants of the bridegroom cannot mourn as long as the bridegroom is with them, can they? But the days will come when the bridegroom is taken away from them, and then they will fast.