What does Luke 5:36 mean?
John's disciples have asked Jesus why His disciples don't fast like they and the Pharisees do (Matthew 9:14). Jesus explains that it's entirely improper to mourn while He is present. There will be a time when He will be taken, and then they will mourn. For now, it's more appropriate to celebrate and feast (Luke 5:33–35).Now, Jesus reveals that fasting is only one of many differences between the life of faith He teaches and the mass of man-made tradition Judaism has become. His message involves the new covenant (Luke 22:20), importantly different from the Mosaic covenant as they practice it. Jesus starts by saying they can't just add parts of what He teaches to Judaism. To do so would nullify the effect of the new covenant because it wouldn't include the heart. And it would tear apart the Mosaic covenant if they attempted to add to it. The point is that Jesus' way can't "patch" the traditions of the Pharisees. They can't use Jesus' ways to cover over worn-out traditions without destroying both.
The book of Acts and Paul's letters give an example. The Pharisees who became Christ-followers wanted to keep their old ways so they would still be welcome in the synagogue. The new way of Christ is that Jews and Gentiles are equally welcome in the fellowship of the church. The Jewish Christians couldn't attend synagogue if they associated with uncircumcised Gentiles. Their solution was to tell the Gentiles they needed to be circumcised. They accepted the "patch" of welcoming Gentiles but damaged it beyond repair by redefining Jesus' way of salvation, which is always by grace, not works, even the work of circumcision (Galatians 6:12–13).
The solution isn't to patch the old Jewish traditions with Jesus' way, but to abandon traditions as paths to righteousness and accept Jesus' new "garment."