NOTES for Mar 2:18-22
In speaking with the Pharisees, who considered themselves guardians of tradition and champions of strict observance of all religious norms and rules, Jesus constantly returns them to the true, original meaning of those norms. The same is true of fasting.
Indeed, the original meaning of fasting in the Semitic world, and therefore among the Jews, came down to mourning, whether mourning for a deceased relative or mourning connected with some tragic event on a national scale. Later, already in the postexilic period, fasting in Judaism also became a sign of repentance for one's personal sins. Still later it turned into a kind of pious religious custom.
Of course, formally the connection between fasting and repentance was preserved in Gospel times, but by then it was precisely and chiefly formal: special days were established for fasting, two during the week, and practically everyone was expected to fast unless he wanted to be known as an impious person and a violator of religious traditions.
Jesus, as we can see, returns fasting to its original meaning: one can and should fast when God leaves and the Kingdom grows distant. But for the inhabitants of the Kingdom, when they experience its life in fullness, fasting is out of the question. The point here is not piety or impiety, but the fact that in this case fasting simply loses its real meaning. What remains is only an external, purely religious formality that in essence has no relation to spiritual life.
But religious formalities are not needed in the Kingdom: by themselves they are spiritually fruitless, and the life of the Kingdom cannot fit into them, just as new wine cannot fit into an old wineskin. The wine ferments, and the worn-out wineskin cannot withstand it. The life of the Kingdom will find new forms for itself on earth, in the world being transformed, in place of the old ones, and there is nothing tragic in this: after all, tradition too has meaning only as an expression and embodiment of spiritual life and spiritual experience. Fasting too is appropriate in its own place and in its own time.
Of course, in a world that is being transformed but has not yet been transformed completely, the inhabitants of the Kingdom will have not only joys, but sorrows as well. There is a time for everything, including fasting. The main thing is that fasting not turn into an empty formality. The same is true of all other religious traditions.