The irony of Mark 2:21–22 cannot be missed: in Jesus’ discussion on fasting, i.e., a practice that abstains from food and drink, He uses the parable of wine to explicate His own meaning. Jesus, in fact, uses two images, first, clothes, then wine, and both of these sensory images help create an even further compelling image of the purpose of fasting.
Both of the short parables here contrast the old and the new. In the first instance, a new “unshrunk cloth” is compared to “an old garment”. Jesus tells us that no one sews a new piece of material sewn onto an old article of clothing. Why? Because “the added piece pulls away…from the old, and the tear becomes worse” (verse 21). Through these sensory details, we learn that not only is the old clothing already torn, but that trying to patch the hole would just make things worse.
In the second instance, new wine is compared to old wineskins. In similar fashion, Jesus states that “no one puts new wine in old wineskins, otherwise the wine will cause the wineskins to burst and the wine will be lost as well as the wineskin” (verse 22). The new wine and the unshrunk cloth have similar effects on old items. Here the old wine holder is not strong enough to hold the new wine; it is already weak and when the new drink is poured in, it falls apart.
But how do these physical images of clothes and wine relate to fasting? The answer lies in their specific type of newness. First, “the unshrunk cloth is presented as new (kainos). This term has a qualitative meaning and recalls ‘the new teaching (kainē; given) with authority’ (Mark 1:27). As for the wine, it is modified by the term neos, which characterizes what is new in the sense of recent, even unexpected. It designates what has just appeared, i.e., the happy announcement by Jesus of the nearness of the reign of God. If we want to mix them, the new will tear the old, the new will cause the old to burst.”
In these two parables, Jesus thus supports his initial statement to the people in Mark 2:18–20. He is telling them that a new reality has come. His arrival has ushered in the beginning of the messianic age. Thus, the old reality – the laws, rules and regulations of the Old Testament, including its prescription on fasting – is worn out. The scribes, the Pharisees, the Sadducees and others may try to resist this change, but it will only lead to disaster, namely greater tearing, holes and bursting (metaphorically and literally). There is no compromise between the old and the new order. There is only submission to Jesus and His teachings (for which this new type of fasting is included) or a reversion to the old ways that leads to destruction.
 Focant, Camille. The Gospel according to Mark: A Commentary. Trans. Leslie Robert Keylock. Eugene, Oregon: Pickwick 2012. Here: P. 107.