When you read the New Testament and concentrate at first on the first three books, you find the life and ministry of Jesus Christ. Matthew, Mark and Luke provide their first hand account of what all Jesus said and did. These gospels indicate that JESUS accomplished many miracles, including casting out devils, demons to be exact that brought about bondage and sickness to people. It was His power as the Son of God who was sinless that gave Him the authority and power to do so. Obviously everyone was astonished and Jesus fulfilled all the prophecies related to him spoken in the Old Testament for that time period.
The demons knew who He was and spoke the same, which He silenced them. He later gave this authority to His disciples to go out and minister as He did; they came back exclaiming their success. Again, later he sent out 70 disciples to do the same thing. Demons bring every disease, sickness and bondage to man, they take up strongholds in our minds and bodies, sometime even a person can be total possessed.(rare but possible)
We have the authority over demons and can cast out demons by faith in our authority. I personally have been doing this for over 30 some years. So DELIVERANCE is a very real exercise in Jesus' name and we have that authority to do so. This takes careful study of the scriptures, faith and obedience. Demons know your strength and can resist your attempts and can be dangerous and harmful if you are not well prepared. There are many studies on this subject for you to learn.
1 John 4:4, Luke 10:19, Romans 16:20, Romans 8:37-39, James 4:7, Ephesians 2:6, Ephesians 6:11, 1 John 3:8, Mark 6:7, Luke 10:17, Matthew 16:19, Matthew 28:18.