Matthew 9:17

17 Nobody pours new wine into old wineskins. If he does that, the new wine will tear the old wineskins. He will lose the wine and the wineskins will spoil. Instead, you must put new wine into new wineskins. Then there will be nothing to spoil the wine or the wineskins.’

9:17Some people kept wine in bottles made from an animal skin. Wine grows as it gets older, but the wineskins become hard. New wine would cause them to break.
9:17Jesus is teaching the people that the old bottles are like the old Law. The new wine and the new cloth are like the new things that Jesus was teaching them. They could not mix the old things and the new things.