Believers have God’s spirit inside of them because they were made pure by the sacrifice of Jesus. They don’t need to be in a ritually clean state to enter God’s presence in a building in Israel anymore, because we are the building (temple). Paul says our bodies are the new temple in 1 Cor 3:16-17, 1 Cor 6:19-20, & 2 Cor 6:15-18. And the Holy Spirit is only available to those who received Jesus as Lord (John 14:15-17, Rom 8:5-11). So how can an unclean spirit ever enter this “new temple” which is the body of a believer?
The Holy Spirit had its first new covenant appearance in Acts 2, and it was described as wind and fire just like God’s presence described in the Old Testament. The same flaming twister that was in the wilderness (Num 9:15-23), fire burning the burning bush (Ex 3:1-5), the blaze on Mt Sinai (Ex19:16-20), and the illuminated presence of God in the Tabernacle hovering above the Ark of the Covenant (Num 7:89, Lev 16:11-13), is the holy spirit. In the old covenant, the fiery presence of God would destroy anyone who wasn’t anointed or ceremonially pure enough to enter his presence (Lev 10:1-7, Num 16:16-35). Now under this new covenant, that presence is inside of believers, to help them overcome their sinful nature. That’s why in Acts 2, smoke and fire appeared. God poured his spirit out on humanity as promised in Joel 2:28-32, and transformed the hearts of his people as Moses prophesied in Deuteronomy 30:6 and Ezekiel in Ez 36:22-27.
When Jesus cast out the demon in Matt 12:22-37, he is criticized by the Pharisees as using the power of Satan, because he can cast them out so effectively. Jesus replied that it doesn’t make any sense for him to use Satan’s power to fight Satan’s kingdom. He asks them where they think their own exorcist gets their power from. He says his power to cast out demons comes from the Spirit of God which proves he is of the Kingdom of God. In verse 29, he sums up what is saying with this, “For who is powerful enough to enter the house of a strong man and plunder his goods? Only someone even stronger—someone who could tie him up and then plunder his house.” The “house” he is referring to in verse 29, is a person’s body and it is demons that enter human bodies and wreak havoc in this context. The only one that can remove a demon is the “stronger man” aka the Holy Spirit. Then he talks about what happens after an exorcism that doesn’t involve the holy spirit in verses 43-45 of the same chapter. He says, “When an evil spirit leaves a person, it goes into the desert, seeking rest but finding none. Then it says, ‘I will return to the person I came from.’ So it returns and finds its former home empty, swept, and in order. Then the spirit finds seven other spirits more evil than itself, and they all enter the person and live there. And so that person is worse off than before. That will be the experience of this evil generation.” We all need the “stronger man” to come in, kick unclean spirits out and stay there so that they can never come back. Believers have the holy spirit and once a person gets saved they cannot be possessed by demons the same way unbelievers do living as puppets and mind slaves.
One last note, in the old covenant, the people had to be ritually pure to come to God’s presence at the Tabernacle/Temple. This meant that God’s presence was so holy that the people had to double-check if they touched a dead body, an unclean person, were menstruating, or had sex recently. If the Israelites couldn’t go near God’s Tabernacle/Temple, in an unclean state, then what makes anyone think that an unclean spirit can go anywhere near the Tabernacle/Temple? Furthermore, if believers are the “New Temple” then no unclean spirit can inhabit the same space as the Holy Spirit. It’s people who are unsaved that need major deliverance and receiving Jesus and the Holy Spirit is by itself deliverance.
The exorcism in the Book of Acts always involved unsaved people. Demons can affect believers just not in the same way as unbelievers because believers have the spirit of God, who can function as a weapon that can be used to overcome. For believers, demons can attack their bodies with ailments, or seduce them through their flesh. However, believers have access to the Holy Spirit and if they chose to live by the Holy Spirit’s leading they can avoid temptation and manipulation by unclean spirits. You’ll notice in the Bible that healing and demonic exorcism are two separate things (Matt 4:24, Matt 10:8) which mean not all sickness and disease come from demons either. In fact, the symptoms of having a demon always involve some kind of neurological problem. Like the woman with the back problem in Luke 13:16, or the boy with seizures that require fasting and prayer (Mark 9:14-29). Other kinds of physical illnesses like bleeding issues, broken limbs, or leprosy were simply sicknesses and not demons.
Some people believe that every sinful temptation is a demon but the Bible doesn’t teach that because sin existed before demons. I believe demons come from the Nephilim and the Giants from Genesis 6. More on the here. However, Cain murdered his brother Abel because of his own sinful desires. James chapter 1:14 does that sin comes from our fleshly desires not unclean spirits.
Lastly, some people suggest that there are physical signs of an exorcism that come along with deliverance like sneezing, yawning, or vomiting. None of the exorcisms in the Gospels or the book of Acts included sneezing, yawning, or vomiting, so none of that related to what Jesus was doing. The only old testament exorcism we see is David playing the harp and soothing King Saul (1 Sam 16:13-23). There is one mention of sneezing in the bible when Elisha raised the widow’s son from the dead (2 Kings 4:35). The boy sneezed seven times when he was revived, but that was a resurrection, not an exorcism, why would seven demons be sitting on a dead body? No resurrection in the rest of the bible old or new testament mentions sneezing or demons. Besides, before the boy died, he had a major headache (2 Kings 4:19), so as far as we know sneezing could have been the body discharging a remnant of a tumor or growth that was destroyed when Elisha revived him. These ideas are commonly taught in certain circles but it’s not consistent with what is written, so I don’t see them as necessary to believe. Exorcism in the Gospels and in Acts involved the holy spirit so ritualistic tools like holy water, cross symbols, and such were not involved, likewise, the only physical sign of a demon leaving was screaming, not sneezing, yawning, or vomiting, and even that wasn’t recorded in all cases. Jesus and his followers just gave a command to leave with the backing of the holy spirit (Mark 1:21-28, Mark 3:11-12, Mark 5:1-20, Mark 6:7, Mark 7:29-30, Mark 16:16-18, Luke 4:33-37, Luke 10:17-20, Luke 13:10-13, Matt 10:1, Acts 5:16, Acts 8:17, Acts 16:16-21, Acts 19:11-12).
If Christians could be possessed as in manipulated like a puppet around by a spirit, they wouldn’t be able to pray to God and would be mindless slaves like the men with the legion in Matthew 8:28-34 or the medium women in Acts 16:16-18. Demonic oppression for believers involves torment stress and anxiety attacks. This is not the same as someone whose mind is being controlled by a demon like a vehicle controlled by a pilot. The Holy Spirit is already inside a believer and they are living temple, preventing a believer from being fully possessed, but because our bodies have sin nature that can function as a bad door and demons can use that to string a believer along by their carnal desires (think carrot and stick). One important for all of this, I am talking about true believers in Christ who actually believe in the bible and have the holy spirit, not apostate Christians that walked away or false teachers that pretend to be Christians to deceive them with teachings that are influenced by other religions. Not everyone who calls themselves a Christian is actually a Christian, many people were raised in Christian culture but don’t actually believe in things the Bible teaches, like special creation in God’s image, resurrection, and eternal life. These are classified as unbelievers, even if they go to a church. There is a difference between going to church and being the church. True believers are filled with the spirit and trust God’s word but they are selectable to demonic influence when they get involved in sin.
Ephesians 6:10 A final word: Be strong in the Lord and in his mighty power. 11 Put on all of God’s armor so that you will be able to stand firm against all strategies of the devil. 12 For we are not fighting against flesh-and-blood enemies, but against evil rulers and authorities of the unseen world, against mighty powers in this dark world, and against evil spirits in the heavenly places.
In Acts ch. 19 we can see the difference between the power of the Holy Spirit that Christians have when fighting demonic power vs what non-believers have. Paul is able to cast demons out with no problem in Ephesus while anti-Christ Jews and pagans failed in their attempts and this causes many pagans to become believers and even burn their spell books.
Acts 19:8 Then Paul went to the synagogue and preached boldly for the next three months, arguing persuasively about the Kingdom of God. 9 But some became stubborn, rejecting his message and publicly speaking against the Way. So Paul left the synagogue and took the believers with him. Then he held daily discussions at the lecture hall of Tyrannus. 10 This went on for the next two years so that people throughout the province of Asia—both Jews and Greeks—heard the word of the Lord. 11 God gave Paul the power to perform unusual miracles. 12 When handkerchiefs or aprons that had merely touched his skin were placed on sick people, they were healed of their diseases, and evil spirits were expelled.
Acts 19:13 A group of Jews was traveling from town to town casting out evil spirits. They tried to use the name of the Lord Jesus in their incantation, saying, “I command you in the name of Jesus, whom Paul preaches, to come out!” 14 Seven sons of Sceva, a leading priest, were doing this. 15 But one time when they tried it, the evil spirit replied, “I know Jesus, and I know Paul, but who are you?” 16 Then the man with the evil spirit leaped on them, overpowered them, and attacked them with such violence that they fled from the house, naked and battered.
Acts 19:17 The story of what happened spread quickly all through Ephesus, to Jews and Greeks alike. A solemn fear descended on the city, and the name of the Lord Jesus was greatly honored. 18 Many who became believers confessed their sinful practices. 19 A number of them who had been practicing sorcery brought their incantation books and burned them at a public bonfire. The value of the books was several million dollars. 20 So the message about the Lord spread widely and had a powerful effect.
Christians have the spiritual power to fight these spirits so believers don’t have to fear them or live in subjection to them. The spirit that lives in a follower of Christ is the same spirit that raised Christ from the dead (Rom 8:11) and is greater than the dark spiritual forces in the world (1 John 4:4).
1 John 4: 1 Dear friends, do not believe everyone who claims to speak by the Spirit. You must test them to see if the spirit they have comes from God. For there are many false prophets in the world. 2 This is how we know if they have the Spirit of God: If a person claiming to be a prophet[a] acknowledges that Jesus Christ came in a real body, that person has the Spirit of God. 3 But if someone claims to be a prophet and does not acknowledge the truth about Jesus, that person is not from God. Such a person has the spirit of the Antichrist, which you heard is coming into the world and indeed is already here. 4 But you belong to God, my dear children. You have already won a victory over those people, because the Spirit who lives in you is greater than the spirit who lives in the world.