In today's gospel we hear the famous parable of the new wine skins and the piece of new cloth. Don't put new wine into old wine skins or new cloth on an old garment as a patch. These things don't work.
Jesus is responding to a question about why the Pharisees fast and his disciples do not. Jesus points out that his teaching is new, he has to teach and train his disciples and that the time for fasting shall come after he is gone. The old Law cannot hold the new dispensation,the new Christian message grows out of the old Law but is so completely new that it fulfills the old Law and requires new action by believers.
So it is with Jesus. He is something new, not that he destroys the old Law but that to see him only in terms of the old is to miss what is completely new!