Then the disciples of John came to him, saying, “Why do we and the Pharisees fast, but your disciples do not fast?” And Jesus said to them, “Can the wedding guests mourn as long as the bridegroom is with them? The days will come when the bridegroom is taken away from them, and then they will fast. No one puts a piece of unshrunk cloth on an old garment, for the patch tears away from the garment, and a worse tear is made. Neither is new wine put into old wineskins. If it is, the skins burst and the wine is spilled and the skins are destroyed. But new wine is put into fresh wineskins, and so both are preserved.”
John the Baptist is probably in prison and his disciples are praying and fasting for his release. You can sense the mournful angst in their question. Jesus speaks to them saying that one day he will, like John, be gone and his disciples will fast in mourning. The first part of his response tries to help John's heartbroken disciples to understand why his behavior, and his disciples, is different from theirs.
Jesus then compares old and new cloth and wineskins to illustrate how there are differences in the old and new covenants. He speaks to the religious practices of the Pharisees implying that they have no place in the new covenant. He is not saying that disciplines like fasting are irrelevant. He is saying that ritualistic rites like fasting are a part of the old covenant. It speaks to me of how the new covenant is not a patch for the old but a replacement of it.
Lord, help me to recognized those old wineskins in my life.