The Bible clearly teaches that evil spirits exist ( James 2:19). They are called "devils" in the King James Version and "demons" in other translations of the Bible. These devils or demons must not be confused with the Devil, Satan, the Tempter (Matthew 4:1-3,10). There is only one Devil, but there are many demons.
In the Bible, we learn that demons entered into people and controlled them (Matthew 8:28-34). They were under the power of Satan (Beelzebub), the chief of all evil spirits (Matthew 12:24). They often caused sickness in the people they entered such as not being able to speak or see (Matthew 12:22); insanity or madness (Luke 8:26-36); personal injuries (Mark 9:18); and other bodily infirmities (Luke 13:11-17).
These demons also knew who Jesus was. They knew why He had come into the world (Luke 4:41). They believe in God (James 2:19). They fear the Judgment and eternal punishment (Matthew 8:29). This clearly shows that demons are not diseases as some have suggested. They are spirit beings who think, speak, and act.
Jesus often cast demons out of people (Matthew 8:16). He also gave the ability to cast out demons to His apostles (Luke 10:17; Mark 16:17,18; Acts 5:16; 8:7; 16:16-18; 19:12). The apostles were able to give miraculous gifts to others by laying their hands on them (Acts 6:6-8; 8:14-21; 19:1-6). This included the power to cast out demons (Acts 8:5-8).
An account of Jesus' casting out a demon is found in Mark 5:1-20. When Jesus came to the country of the Gadarenes, a man met him. He had an "unclean spirit" (demon). This demon possessed man lived in the tombs. He wore no clothes. He was not in his right mind. He cried day and night and cut himself with stones. He also had great strength. When others had bound him with chains, he broke them and escaped. The evil spirit in the man knew who Jesus was and begged Him not to torment him. Jesus asked the evil spirit, "What is your name?" He replied, "My name is Legion; for we are many." When Jesus commanded the demons to come out of the man, they begged him to send them into pigs who were feeding nearby. Jesus did so. The pigs ran to the cliff, fell into the sea, and drowned. When the people of the area came to Jesus, they saw this man "sitting, clothed, and in his right mind." When the demon was cast out, the man was restored to health of body and mind.
Do demons still possess people even today? Zechariah, an Old Testament prophet, spoke of the time when Christ would come. He said: "In that day a fountain shall be opened for the house of David and for the inhabitants of Jerusalem, for sin and for uncleanness" (Zechariah 13:1). This fountain was opened when Jesus shed His blood on the cross for the sins of the world. Zechariah then said: "It shall be in that day, says the Lord of hosts, that I will cut off the names of the idols from the land, and they shall be no longer remembered. "I will also cause the prophets and the unclean spirits to depart from the land" (13:2). Following the time when the Lord would die for our sins, prophets (men who spoke by the Holy Spirit) and unclean spirits (demons) would no longer be in the land (earth). When did this happen?
We have learned that the apostles could give to others the ability to work miracles. The purpose of these miracles was to confirm ( prove) God's Word (Mark 16:20: Hebrews 2:2-4). Paul said these gifts of the Holy Spirit would fail, cease, and vanish away (1 Corinthians 13:8-10). These miraculous gifts would cease when that which is perfect has come (v.10). This refers to the New Testament, which is called the perfect law of liberty (James 1:25). One of these gifts was the power to cast out demons. Therefore, evil spirits possessing men, along with the power to cast them out, ceased when the New Testament was completed and confirmed. If demon possession continued today, Satan would have more power than God, for he could send his demons into people, but God's people could not cast them out.
God permitted demons to possess certain people in the time of Christ and the apostles so that His power could be seen. Not only did Christ have power over nature, disease, and death, but He also had power over the spirit world. The Devil and his demons were proved to be powerless before the Son of God (Colossians 2:15; 1 John 3:8). Demons still exist, but they do not possess people today. Today, we need to be concerned about Satan, the Devil, who tempts us to sin (James 1:14; Matthew 4:3; 1 Peter 5:8).