If Satan already fell from heaven, why does Revelation 12:7 refer to Satan being cast out of heaven?

Answer

Satan is a fallen angel, and his initial sin and expulsion from heaven are recorded in poetic form in Isaiah 14:12–15 and Ezekiel 28:12–15. Jesus refers to this event in Luke 10:18: “I saw Satan fall like lightning from heaven.”

But it seems that, even after his fall, Satan still has access to heaven, at least on a limited basis. In the first two chapters of Job, Satan appears before God along with other angelic beings: “One day the angels a came to present themselves before theLord, and Satan also came with them” (Job 1:6). Satan uses his audience with God to accuse Job (verses 9–11; cf. 2:4–5). It seems that Satan’s presence in heaven was based on God’s summons, but he was there nonetheless.

The book of Revelation gives us another event to add to Satan’s timeline:

Now war arose in heaven, Michael and his angels fighting against the dragon. And the dragon and his angels fought back, but he was defeated, and there was no longer any place for them in heaven. And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him. (Revelation 12:7–9, ESV)

So, the Bible describes more than one “casting down” of Satan. God’s judgment of Satan occurs in different stages through history. Although Satan is already cast out of heaven in some sense today, there is coming a time when he will be completely barred from heaven. This will happen during the tribulation, probably at the midpoint of those seven years. The result of Satan’s being confined to earth is not good news for inhabitants of the earth: “Woe to the earth and the sea, because the devil has gone down to you! He is filled with fury, because he knows that his time is short” (Revelation 12:12).

Here are the progressive stages of Satan’s rebellion and God’s judgment upon him:

Satan’s Original Fall. Lucifer held a lofty position as one of God’s holy angels, but sin entered his heart and he became a fallen being (Isaiah 14:12–15; Ezekiel 28:12–17). He lost his position in heaven and his original glory. This is his moral fall, after which Satan is still allowed to approach God’s throne on a limited basis. There he acts as the “accuser of the brethren” (Revelation 12:10). Scripture records him accusing Job (Job 1—2) and Joshua, the post-exilic high priest (Zechariah 3:1–2).
Satan’s Defeat at the Cross. Shortly before His arrest and crucifixion, Jesus said, “Now is the time for judgment on this world; now the prince of this world will be driven out” (John 12:31). When Jesus died and rose again, Satan’s power was judged—Satan lost the legal right to accuse those redeemed by the blood of Christ. See also Colossians 2:15.
Satan’s Future Expulsion from the Heavenly Realms. During the Great Tribulation, Michael and his angels will battle Satan and his angels. The holy angels win, and the dragon and his angels will lose their place in heaven once and for all; they will no longer be granted access to heaven. At that time, Satan will be confined to the earthly realm (Revelation 12:7–9).
Satan’s Final Judgment. Satan’s fate is to be cast into the lake of fire, where he will remain forever (Revelation 20:10). This will take place after the millennial reign of Christ on earth. After this judgment, the devil will never be seen again.

So, while Satan has already fallen morally and legally, Revelation 12 shows another fall (to earth), and Revelation 20 shows the final fall, into the lake of fire. Believers in Jesus Christ can take heart that Satan’s defeat is certain. Christ’s death and resurrection have sealed the devil’s doom (Colossians 2:15). Satan’s accusations no longer st and (Romans 8:1, 33–34). The believers’ defense is Christ’s finished work and His intercession (Hebrews 7:25). Satan’s final confinement is coming, and believers will be among those who “triumphed over him by the blood of the Lamb and by the word of their testimony” (Revelation 12:11).