The answer
Our Lord Jesus Christ had given His apostles and disciples the power to cast out demons in His name while He Himself was still on earth (Matthew 10:1,8; Mark 6:7; Luke 9:1; 10:17). This power was given not only to the Apostles, but also to believers "And these signs will follow those who believe: In My name they will cast out demons" (Mark 16:17) However, the effectiveness of this given power was conditional. The apostles themselves were not always successful in their practice of exorcism (Matthew 17:15-21; Mark 9:27-28; Luke 9:40). In other words the practice of exorcism successfully by Christians, in Christ's name, depends on the efficacy of prayer, the work of grace and other virtues granted to every Christian for the purpose of performing this task.Answered by His Eminence Metropolitan Youssef (opens in a new tab)