One of the prominent features of Jesus' earthly ministry was the casting out of demons. It clearly demonstrated Christ's power over sin, death and the devil. And there was nothing Satan or his demonic cohorts could do to stop it.
Here are some examples:
When evening came, many who were demon-possessed were brought to Him, and He drove out the spirits with a word and healed all the sick. Matthew 8:16
Some distance from them a large herd of pigs was feeding. The demons begged Jesus, "If you drive us out, send us into the herd of pigs." He said to them, "Go!" So they came out and went into the pigs, and the whole herd rushed down the steep bank into the lake and died in the water. Matthew 8:30-32
A man who was demon-possessed and could not talk was brought to Jesus. And when the demon was driven out, the man who had been mute spoke. Matthew 9:32,33
Jesus healed many who had various diseases. He also drove out many demons, but He would not let the demons speak because they knew who He was. Mark 1:34
So Jesus traveled throughout Galilee, preaching in their synagogues and driving out demons. Mark 1:39
In the synagogue there was a man possessed by a demon, an evil spirit. He cried out at the top of his voice, "Ha! What do you want with us, Jesus of Nazareth? Have you come to destroy us? I know who you are - the Holy One of God!" "Be quiet!" Jesus said sternly. "Come out of him!" Then the demon threw the man down before them all and came out without injuring him. Luke 4:33-35
Demons came out of many people, shouting, "You are the Son of God!" But He rebuked them and would not allow them to speak, because they knew He was the Christ. Luke 4:41
Jesus said, "If I drive out demons by the finger of God, then the kingdom of God has come to you." Luke 11:20
And so we see in Scripture that demons must obey Jesus because He has authority over them. Demons are fallen angels who are terrified of Christ because they know He is the Son of God. And it was the Lord who kicked these rebels and their leader out of heaven.
After the Lord appointed disciples to go out two by two, "The seventy-two returned with joy and said, 'Lord, even the demons submit to us in your name.' Jesus said, 'I saw Satan fall like lightning from heaven.'" (Luke 10:17,18) The coup attempt led by Lucifer clearly failed. No surprise there, especially since created beings possess far less power and authority than our Creator.
Nevertheless, Satan holds plenty of sway over unbelievers. The apostle Paul wrote, "The god of this age has blinded the minds of unbelievers, so that they cannot see the light of the Gospel of the glory of Christ, who is the image of God." (2 Cor. 4:4)
So why didn't Jesus and the apostles just "cast out" unbelief the way they cast out demons? Wouldn't that approach have allowed the blind to see Christ, especially since "the god of this age" (Satan) is responsible for "blinding the minds of unbelievers"?
Scripture reveals that casting evil spirits out of those who are demon-possessed is not the same thing as leading a person from unbelief to faith in Christ. Both demon possession and unbelief have the fingerprints of Satan all over them, but Jesus never instructed His followers to "cast out" unbelief the way they cast out demons.
Instead, the Lord sent His disciples out so that "repentance and forgiveness of sins will be preached in Christ's name to all nations." (Luke 24:47) It is the preaching of the Gospel that "casts out" unbelief whenever a sinner repents and believes the good news. And much prayer is needed when spreading the Gospel because this critical endeavor is strongly opposed by "the spiritual forces of evil in the heavenly realms." (Eph. 6:12)
When moving from unbelief to faith in Jesus, a person turns from sin and receives the free gift of salvation. (Romans 6:23) This turning and receiving is not something God forces anyone to do, whereas demons have no choice when they are driven out of someone in the name of Jesus. Unbelief isn't "cast out" apart from repentance and faith in Christ. Spiritual conversion is a mighty miracle of the Holy Spirit (John 3:6) involving a sinner turning from sin and relying upon Christ for salvation. Believers are saved by grace through faith. (Eph. 2:8,9) Spiritual eyes are opened through the preaching of the Gospel and the power of God. (Acts 2:14-41)
Likewise, casting out demons demonstrates the power of Christ over Satan as people are delivered out of darkness into the light. When Jesus called and commissioned Saul to become the apostle Paul, He told him: "I am sending you to open their eyes and turn them from darkness to light, and from the power of Satan to God, so that they may receive forgiveness of sins and a place among those who are sanctified by faith in me." (Acts 26:17,18)
Paul would later write, "I am not ashamed of the Gospel, because it is the power of God for the salvation of everyone who believes." (Romans 1:16) Salvation is a free gift that removes the sin of unbelief from the hearts of those who receive Christ by faith. "Yet to all who received Him, to those who believed in His name, He gave the right to become children of God." (John 1:12) Spiritual conversion delivers the soul from the clutches of Satan forever, and nothing is better than spending eternity with the Lord in Paradise.
If you are in need of deliverance today, Jesus can definitely set you free. And your unbelief will be replaced with faith the moment you trust Christ as Savior. Simply "repent and believe the good news." (Mark 1:15) After all, "Christ died for sins once for all, the righteous for the unrighteous, to bring you to God." (1 Peter 3:18) "Believe in the Lord Jesus, and you will be saved." (Acts 16:31)