There are good reasons for fasting but I never understood the Pharisees' question to Jesus, as it always seemed to ask why he wasn't copying the "holy crowd." Surely that would be the last reason for doing it ... which is just what Jesus points out. This is especially true when we know more about fasting in those times.
With the stricter Jews fasting was a regular practice. In the Jewish religion there was only one day in all the year that was a compulsory fast, and that was the Day of Atonement. The day when the nation confessed and was forgiven its sin was The Fast... But the stricter Jews fasted on two days every week, on Mondays and Thursdays. It is to be noted that fasting was not as serious as it sounds, for the fast lasted from 6 a.m. to 6 p.m. and after that normal food could be eaten...You may recall that I brought up the Pharisees questioning the disciples about Jesus' hanging out with sinners. Now, let's take another quick look at how the question about fasting is handled.
... The trouble about the Pharisees was that in far too many cases their fasting was for self-display. It was to call the attention of men to their goodness. They actually whitened their faces and went about with disheveled garments on their fast days so that no one could miss the fact that they were fasting and so that everyone would see and admire their devotion. It was to call the attention of God to their piety. They felt that this special act of extra piety would bring them to the notice of God. Their fasting was a ritual and a self-displaying ritual at that...
The Gospel of Mark (The Daily Bible Series*, rev. ed.) by William Barclay
Once again, those voicing criticism aim it indirectly, as if seeking to drive a wedge between Jesus and his followers. Where as the previous question about Jesus had been addressed to his disciples (Mark 2:16), now a question about his disciples is addressed to Jesus.Interesting isn't it? What I always saw as fairly straight forward questions, albeit angry ones with ulterior motives, now become something much more planned and sly. The Gospel of Mark has a subtlety that it often isn't credited with and which Healy's commentary helps me to appreciate.
The Gospel of Mark: Catholic Commentary on Sacred Scripture by Mary Healy
* Not a Catholic source and one which can have a wonky theology at times, but Barclay was renowned for his authority on life in ancient times and that information is sound, as are many of his general reflections.