Dear Dian:

This is a famous passage in the world of Deliverance Counseling. I use this passage all the time in my teaching and with my clients who are demonized. The Ignatius Study Bible commentary does a good job of explaining this passage:

[This is] a parable about Jesus' generation. It may be understood in two ways. (1) It is a warning to those who benefit from Jesus' ministry without embracing his message and its demands. Since one must be not only emptied of evil but filled with divine goodness, the messianic works of Jesus should lead people to accept his messianic kingdom; otherwise a land themselves in a worse state than before (2 Peter 2:20-22). (2) The controversy over exorcisms in the preceding context (12:22-29) sets the stage for Jesus to establish the superiority of his New Covenant ministry over the Old administered by the Pharisees. Although the Pharisees expel evil spirits ("your sons" [12:27]), they leave a vacuum that exposes individuals to more severe counterattacks from Satan. Jesus also drives out demons, but, unlike the Pharisees, he fills believers with the greater power of his kingdom to his spirit (12:28). Jesus' contemporaries must refer these blessings of his kingdom ministry to the real but limited benefits of the Pharisees' ministry; otherwise the are left vulnerable to spiritual catastrophes worse than before.

What all this means is that we can get rid of the cockroaches (demons) in our house, and clean our house so that the cockroaches will not be attracted to come back. But, if we leave the house empty, even though everything is put an order and clean, when the demons check on the house and find it empty they will come back most often with more demons more hideous than the first — the house being empty of anything to prevent them from re-infesting it.

The "house empty" refers to the need for the house owner to not only kill the cockroaches, and to clean his house and get it in order, but he also needs to fill the house with the Holy Spirit, which is done by living the Christ-life in a state of grace. As it says in a commentary, "Jesus also drives out demons, but, unlike the Pharisees, he fills believers with a greater power of his kingdom through the Spirit."

Thus, if we are being harassed by demons we need to do what is necessary to expel those demons from our house, we need to clean the house and get it in order so that the demons are not attracted to come back, and then we need to fill the house with the Holy Spirit by living the Christ-life in a state of grace so that if the demons do come back to check on us there is a barrier to prevent them from entering. It is then that we have the greatest success of keeping our household free from demonic harassment and infestation.

God Bless,
Bro. Ignatius Mary