Christians have authority over Satan, but it is not their own authority that overcomes Satan; it is the authority of Christ within them that has the power to overcome Satan.
What authority do Christians have over Satan?
God is the Creator of all things and His power is limitless and perfect in its nature, just as He is (Genesis 1:1). God has power over life and death (1 Samuel 2:6) and He has total power over Satan. In the end, He will cast Satan into the lake of fire for eternity (Revelation 20:7–10).
Satan has strong power, but it is nothing in comparison with God's. The first demonstration we see of Satan wielding his evil powerful influence is in the garden of Eden when he convinces Eve to eat from the Tree of the Knowledge of Good and Evil (Genesis 3). Satan tempted Jesus while He was fasting in the wilderness, but he could not get Jesus to sin (Matthew 4:1–11). Satan's primary power is the power of influence that we give him in order to deceive us and keep us under the power of sin rather than under the power of God (2 Corinthians 11:3; 2 Thessalonians 2:8–12).
Jesus healed a crippled woman who was under the power of an evil spirit from Satan: "And behold, there was a woman who had had a disabling spirit for eighteen years. She was bent over and could not fully straighten herself. When Jesus saw her, he called her over and said to her, 'Woman, you are freed from your disability.' And he laid his hands on her, and immediately she was made straight, and she glorified God" (Luke 13:11–13). This shows that even though Satan had great power over this woman for eighteen years, it only took one encounter with Jesus for her to be freed. Satan is referred to as "the ruler of this world," but when Jesus returns He will cast Satan out once and for all (John 12:31).
So, how exactly do these factors affect believers' power over Satan? When we believe in Jesus Christ (John 3:16; Ephesians 2:8–9), we are indwelled with the Holy Spirit and this is how we have power over the Devil. Galatians 2:20 says, "I have been crucified with Christ. It is no longer I who live, but Christ who lives in me." The same God who created the universe lives within us. When we live in submission to God's Spirit, we have power over Satan, because the power of Christ operates in and through us. Satan cannot overcome believers in Christ, because Satan cannot defeat the Spirit of God that inhabits them.
This does not mean Satan will not try to harm us. The Bible instructs us: "Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour" (1 Peter 5:8). Satan will attack and deceive; he will be seeking an inroad into our lives. This is why as Christians, we are to: "Put on the whole armor of God, that you may be able to stand against the schemes of the devil. For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places" (Ephesians 6:11–12). As Christians, while we may still struggle with evil and the temptation to sin, we have the power to resist Satan and his temptations when we are living in submission to Christ. Satan will flee when we resist him in Jesus' name (James 4:7; 1 John 4:4).
In and of ourselves, we have no authority over Satan. This is why we see non-believers living under the power of Satan, unable to resist sin. However, when we believe in Jesus Christ, His power that lives within us fights on our behalf. We are able to say "no" to sin, live holy lives, and be protected by God. When Jesus was tempted by Satan, He responded by quoting the Word of God (Matthew 4:1–11). Jesus is our example, so we, too, can defeat the Devil by the power of the Word of God (Ephesians 6:17). In the end, because Jesus has all authority in heaven and earth, we will have total victory over Satan (Romans 16:20).
Can Christians rebuke the devil? Do Christians have authority to rebuke Satan?
How does a person resist the Devil? Why does resisting the Devil cause him to flee?
How should I respond to spiritual attack?
What is the full armor of God?
God vs. Satan? If He is really all-powerful, why doesn't God just kill Satan?
Truth about the Christian Life