Question: "What does it mean to resist the devil, and why will resistance cause the devil to flee?"
Answer: The phrase “resist the devil” is found in James 4:7 where the apostle James exhorts believers to resist the devil in order to cause him to flee or “run away” from us. To resist means to withstand, strive against, or oppose in some manner. Resistance can be a defensive maneuver on our part, such as resisting or withstanding the temptation to sin. Or it can be an action we take to use the only offensive weapon in the full armor of God (Ephesians 6:13-18), the sword of the Spirit which is the Word of God. Using the Scriptures to expose Satan’s lies and temptations is the most effective way to strive against and defeat them.
It is important to read the whole verse: “Submit yourselves, then, to God. Resist the devil, and he will flee from you” (James 4:7). Resisting the devil must be accompanied by submitting to God. A disobedient or unsubmissive believer will not see victory.
The apostle John records Jesus saying about Satan, “The thief comes only to steal and kill and destroy; I have come that they may have life, and have it to the full” (John 10:10). As Christians, we have full life when we are aware of the reality of the presence of evil. As we struggle to stand firm in our faith, we must realize that the enemies we are up against are not merely human ideas, but real forces that come from the powers of darkness. The Bible says, “For our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the heavenly places” (Ephesians 6:12).
Why will resistance cause the devil to flee? Because he knows he cannot have victory over us if we are prepared to do battle against him. As mentioned before, the Bible assures us that we need only put on the full armor of God to be fully protected from evil and to actively resist it. There is nothing more frightening to Satan than a believer who is fully equipped with spiritual armor, beginning with the “helmet of salvation,” which protects our minds, and the “breastplate of righteousness,” which protects our hearts because it is the righteousness of Christ (2 Corinthians 5:21). Only a true believer wears these because only those who have received God’s forgiveness by grace through faith have eternal salvation and the righteousness of Christ imputed to them.
Once fitted with the helmet and breastplate (literally, “chest protector”), we are then to take up other defensive weapons with which to battle Satan: truth, the readiness to proclaim the gospel, and the faith that shields us from all the flaming arrows of the evil one. The final piece of armor is prayer. We pray for strength to resist evil and to actively battle against it. We pray for wisdom in the conflict, and most of all, we remain steadfast in our prayers, both for the ability to resist the devil and also for other believers who struggle in the same battle. When the church, the body of Christ, stands united against evil, fully equipped with the armor of God, we present a formidable foe to the evil one and we will see God get the glory for the victory.
As a side note, the Bible never gives Christians the authority to “rebuke” the devil, only to resist him. Zechariah 3:2 tells us that it is the Lord who rebukes Satan. Even Michael, one of the most powerful of the angels, did not dare to accuse Satan, but rather said, "The Lord rebuke you" (Jude 1:9). In response to Satan's attacks, Christians should redouble our efforts to clothe ourselves in the spiritual armor, wield the Word of God, and rely on His power through prayer. Instead of focusing on “rebuking” the devil, we should focus on resisting him with the full armor of God.