Matthew 9:14-17 ASV

God is patient for the right faith (wine) in us to be ready for his promises (wineskins). If I'm not ready for a blessing or promise God is patient in his own time, otherwise the blessing would be an even greater curse/temptation (tear, bursting to ruin).

The Pharisees wanted the disciples of Jesus to fast, but the disciples' faith was on the new promise of Jesus. The Pharisees weren't ready in their faith and hearts for Jesus, so they couldn't celebrate his presence. At the same time the disciples new the promise that was before them, and to step backwards would have been just as bad.

This verse isn't as much a condemnation of the Pharisees in regards to where their faith was, though they were obviously lacking a faith that listened for and to the heart of God. The rebuke was that they wanted the disciples faith and practice to be the same as their own, for self-validating purposes.