What does Matthew 9:17 mean?
Jesus is presenting three illustrations to answer one question: Why don't your disciples fast, as did the Pharisees and the disciples of John the Baptist (Matthew 9:14)? This is Jesus' third of three illustrations in response (Matthew 9:15–16). Christ describes why His arrival on earth has changed how many things will be practiced and understood by the people of God.Wineskins in this era were created from the skins of animals. When a wineskin was first cleaned and tanned and made ready for use, it was flexible and stretchy. It could expand as the liquid inside of it fermented and gave off gases during the transformation into wine. An old wine skin, though, had lost its flexibility. It became brittle. Being closed off for another fermentation process would cause that skin to split as pressure built, spilling the wine and destroying the skin.
Jesus is saying His arrival on earth as the Messiah, the bridegroom (Matthew 9:15), has begun the new era of the kingdom of heaven. The old ways of Judaism are the old wineskin. The ways of the kingdom will not fit into those old religious practices and observances. New ways are coming that will be practiced by those, Jew and Gentile alike, who come to God through faith in Jesus.
In other words, Jesus was not going to fit the ways of His kingdom into the ways of Judaism to make some kind of hybrid religion. He was starting something new. Implied in this is that Jesus' disciples would not fast while He was with them preparing this new way of coming to the Father through faith in Him. As He said in verse 15, however, they would fast for a time, after He was taken away.