Jesus' approach to casting out demons was a big puzzle for those who did not want to welcome Him as the Son of God. They questioned His authority, and even suggested that He used Satan's power to remove evil spirits (Luke 11:15).  Then Jesus told them a story: He wanted them to think about what happens after the demons make their exit.  God always works to perfection, and does not remove evil just to allow more evil to invade a person.

The evil spirit is depicted as a wanderer looking for a place to rest.  When somebody has been delivered from demonic terrorisation and manipulation, that is not the end.  What happens next is most important because it sets the pattern for the future.  If the demon's place is not occupied by God, evil will find it a comfortable place to reinvade, and with worse consequences than before.  The point Jesus was making is this: removing the terror of evil is only half of the job - the other half is to fill the person with the life of God, and only Jesus could do that.

We may pray to be delivered from evil, but if we do not actively seek the filling of God's holy presence, we leave ourselves exposed in a dangerous way.  The Lord Jesus is not just a collector of our rubbish but a person who eagerly desires to live in us with full authority to rule over every area of our lives (Ephesians 3:17).  His Holy Spirit is the only person who can fill the void left by the presence of evil in our lives.   

Many would like the discomfort of wickedness removed so that they can get on with their selfish lives undisturbed, but without the undiluted presence of God, fresh disturbance will come.  We lead men and women to the Lord, not just for their healing but so that they may become wholehearted disciples of Jesus Christ and filled with His Spirit so that they may serve Him and give no place to the devil (Ephesians 4:27).