First of all, we need to ask the question, “What is a demon?” Vines Dictionary says that “In the New Testament it denotes as EVIL SPIRIT.” Luke 7:21 says, “And that very hour He cured many of infirmities, afflictions, and EVIL SPIRITS; and to many blind He gave sight” (NKJV). These evil “spirit-beings” love to possess the bodies of men and Jesus cured many who were possessed by casting them out. This is confirmed in Matthew 8:16: “When evening had come, they brought to Him many who were demon-possessed. And He CAST OUT THE SPIRITS with a word.” They are also referred to as “unclean spirits” in many passages, such as Mark 1:27: “Then they were all amazed, so that they questioned among themselves, saying, ‘What is this? What new doctrine is this? For with authority He commands even the UNCLEAN SPIRITS, and they obey Him.”

We have no doubt that demons are “angels,” for Scripture tells us that angels are “spirits” in many places. Hebrews 1:7 declares, “And of the angels He says, ‘Who makes His angels spirits and His ministers a flame of fire.” Yet as we have seen, demons are “evil” and “unclean” and this implies that they are “fallen angels” who at one time were “good spirits” (when God first created them) but now they are “evil spirits.” So, now we are prepared to answer your question, “What is the origin of demons?” or put another way, “When did these angels fall and become demons?

In Revelation 12:9 we read, “So the great dragon was cast out, that serpent of old, called the Devil and Satan, who deceives the whole world; he was cast to the earth, AND HIS ANGELS were cast out with him.” This is a prophecy describing Satan’s expulsion from heaven during the coming tribulation period and it teaches us that he “and his angels” will be cast out. In a minute we will show scriptures that reveal “the origin of Satan,” but our present verse brings out clearly that Satan is the ruler among these fallen angels. In Matthew 9:34 the Pharisees made this accusation against the Lord Jesus, “He casts out demons by the ruler of demons.” We conclude then that the “origin of Satan” and the “origin of demons” occurred at the same time.

There are two passages of Scripture which describe the “origin of Satan.” The first is Isaiah 14:12-14: “How you are fallen from heaven, O Lucifer, son of the morning! How you are cut down to the ground, You who weakened the nations! For you have said in your heart: ‘I will ascend into heaven, I will exalt my throne above the stars of God…I will ascend above the heights of the clouds, I will be like the Most High’.” Here we learn that Satan was once called “Lucifer, son of the morning,” implying that he was once one of God’s greatest creations. Yet we see here that he defied God and wanted to sit on His throne in heaven. At that very moment he became, as we saw in Revelation 12:9, “the Devil and Satan.” We learn something else about him in Ezekiel 28:12: “Thus says the Lord GOD: ‘You were the seal of perfection, Full of wisdom and perfect in beauty.” He was created in absolute PERFECTION, WISDOM and BEAUTY. But verse 15 goes on to say, “You were perfect in your ways from the day you were created, TILL INIQUITY WAS FOUND IN YOU.” What was this “iniquity” that was found in him? The answer is in verse 17, “Your heart was lifted up because of your beauty; You corrupted your wisdom for the sake of your splendor.” In a word, PRIDE filled Lucifer’s heart and caused him to rebel against God by desiring, as we saw in Isaiah 14, to dethrone God and to sit on God’s throne.

It is an obvious conclusion that the “demons” had their origin at the same time; in other words they followed Lucifer in his rebellion and thus became “evil” and “unclean” spirits. Some commentators believe that one third of all the angels of heaven were so influenced by Satan that they willingly aligned themselves with him. Revelation 12:4 is used to support this view. It says, “His [the great dragon, Satan] tail drew a third of the stars of heaven and threw them to the earth.”  (216.3) (DO)