Jesus began Luke chapter 11 giving us an example of prayer. He continued teaching his disciples that God is keenly interested in giving his people what they need, but that they must also keep asking him, keep seeking him and keep knocking on the door.
After the Pharisees accused Jesus of casting out demons by the prince of demons, the Lord turned to them and told them that if that were true, they had nothing to worry about: he was sure to fail. But if what he was doing had God’s approval, then the kingdom of heaven had truly come.
Though it seems that Jesus changes the subject later in verses 24-28, he had not. The Pharisees’ main problem was that they looked impressive on the outside, but inside they were filled with dead men’s bones (Matthew 23:27).
It is truly good to repent of sin, but if we leave our hearts fallow, evil will find a way to enter us. The solution for the unclean spirit of Luke 11:24 was to return to a house that had been swept and put in order. Only the return marked a serious problem in that “the last state of the man is worse than the first.”
Why is that true? Think of Newton’s laws of motion. Truck makers don’t put automobile brakes on a large tractor-trailer. There’s too much mass involved. The truck will never stop in time. It will become much more difficult if, once we’ve obeyed God, we return to the practice of sin. We may never find a way to stop and may die lost.
One commentator has written, “History relates that those who had rejected Christ in Israel were worse off due to their rebellion. Ultimately their rejection resulted in the destruction of Jerusalem and the temple in A.D. 70.”
We must take special care not only to get rid of the evil in our hearts, but also make certain good things, deeds, and works fill the empty space.
 “Truth-for-Today Commentary, Volume 1, Matthew 1-13 by Sellars Crain, Jr., D.Min page 417.