Jesus illustrates being persistent in prayer. Prayer is not magic. Prayer informs God and it forms the person. Sometimes God says, "Yes," sometimes, "No," and sometimes, "Not yet." Persistence shows we really want something and have given it thought.
Jesus is accused of doing good by working for the devil (or evil.) Jesus points out how dumb a notion that is. He also points out that filling ourselves with God prevents more evil from returning. It is not enough to heal; we must rely on god as well.
Jesus scolds the people for wanting magic (signs) without faith. Jesus says that it does not work that way. Signs are not for amusement but are the fruit of faith. If we want proof that he is real, bet our life on it by investing in God! No other proof than that which we invest in will come.
Jesus really lets the religious people have it when he says they look good on the outside but are rotten on the inside. Actors are not what God wants. Healthy and whole people are ones who take to heart the things Jesus says and acts on them. More over, the religious people lay pointless burdens on people backs. They are discouragers of faith and not encouragers.