There is strong biblical evidence that a Christian cannot be demon possessed. The question then arises regarding what influence/power a demon can have over a Christian. Many Bible teachers describe demonic influence on a Christian as “demonic oppression” to distinguish it from possession.
The Bible says that the devil seeks to devour believers (1 Peter 5:8), and Satan and his demons “scheme” against Christians (Ephesians 6:11). As Satan attempted with Jesus (Luke 4:2), demonic forces tempt us to sin and oppose our efforts to obey God. Should a Christian allow the demons to succeed in these attacks, oppression results. Demonic oppression is when a demon is temporarily victorious over a Christian, successfully tempting a Christian to sin and hindering his ability to serve God with a strong testimony. If a Christian continues to allow demonic oppression in his/her life, the oppression can increase to the point that the demon has a very strong influence over the Christian’s thoughts, behavior, and spirituality. Christians who allow continuing sin open themselves up for greater and greater oppression. Confession and repentance of sin are necessary to restore fellowship with God, who can then break the power of demonic influence. The apostle John gives us great encouragement in this area: “We know that anyone born of God does not continue to sin; the one who was born of God keeps him safe, and the evil one cannot harm him” (1 John 5:18).
For the Christian, the power for victory over and freedom from demonic oppression is always available. John declares, “The One who is in you is greater than the one who is in the world” (1 John 4:4). The power of the indwelling Holy Spirit (Romans 8:9) is always available to overcome demonic oppression. No demon, not even Satan himself, can prevent a Christian from surrendering to the Holy Spirit and thereby overcoming any and all demonic oppression. Peter encourages believers to resist the devil, “standing firm in your faith” (1 Peter 5:9). Being firm or steadfast in the faith means relying on the power of the Holy Spirit to successfully resist demonic influence. Faith is built up through the spiritual disciplines of feeding on the Word of God, persistent prayer, and godly fellowship. Strengthening our faith by these means enables us to put up the shield of faith with which we can “extinguish the flaming arrows of the evil one” (Ephesians 6:16).