There is no substitute for the ministry of deliverance. The freedom that comes from casting out demons enables believers to rise to new levels of faith and obedience. It also opens the way for evangelism. The controlling powers of darkness are neutralized, and more people respond to the preaching of the gospel. It is a key to opening up entire regions to be evangelized. The heavens are opened, and the blessings of God are released.
Deliverance is necessary to attack and drive out religious spirits that have aborted and hindered much of what God desires to do. Spirits of witchcraft and generational spirits must also be challenged and driven out. Deliverance opens the way for holiness. Cleanliness and purity must be in place to keep the church from being diverted from its course.
…John Eckhardt, Ordinary People, Extraordinary Power, 95.