There isn’t a lot said about what happened in Heaven when Lucifer was cast out, but what was said gives an interesting picture.
Isaiah 14:11 All your pomp has been brought down to the grave,
along with the noise of your harps;
maggots are spread out beneath you
and worms cover you.
12 How you have fallen from heaven,
O morning star, son of the dawn!
You have been cast down to the earth,
you who once laid low the nations!
13 You said in your heart,
“I will ascend to heaven;
I will raise my throne
above the stars of God;
I will sit enthroned on the mount of assembly,
on the utmost heights of the sacred mountain.
14 I will ascend above the tops of the clouds;
I will make myself like the Most High.”
15 But you are brought down to the grave,
to the depths of the pit.
So, in his heart he had pride and thought to over throw the kingdom of God. He wanted to rebel against God’s authority. So why did 1/3 of the angels in Heaven get cast out with him? Did they believe that Lucifer was greater than God, or did they actively participate in the rebellion against the kingdom.
It is God’s kingdom, so God has authority over the kingdom and those who are in the kingdom. Either you are obedient and follow the authority or your not and rebel against the authority. Lucifer and his followers moved against the authority of God and were cast out. The prideful thought gave way to the action, but it was the action that caused his removal. The interesting part is Lucifer did not lose his authority over those that were under him while in heaven.
Jude 1:9 But even the archangel Michael, when he was disputing with the devil about the body of Moses, did not dare to bring a slanderous accusation against him, but said, “The Lord rebuke you!”
When you are in a position of authority, you can bring the accusation or judgment against one beneath you. Lucifer was the head of the angels, yet he could be rebuked by the authority of the Lord. We know that Jesus (the Lord) is above Lucifer in authority and that Jesus and Michael are not the same.
When Adam and Eve sinned and were cast out of the garden, what was the sin? Satan told them they would be like God if they ate. Seems like pride, but it wasn’t the thought that got them kicked out. It was the act of disobedience that was the offense. If it was only the thought that was the sin, wouldn’t God have called them on it when it first entered into her mind? So Adam and Eve disobeyed God.
Islam differs here with Christianity / Judaism in that Islam says there is no original sin. The sin is not passed down from generation to generation. Instead, the Quran says that Adam and Eve repented and God forgave them. The Bible doesn’t really disagree with this. You see a blood sacrifice being made and Adam and Eve clothed in animal skins. The Bible doesn’t come out and say there was a sacrifice, but God had to kill something in order to get animal skins to make clothes.
I think the original sin gets misconstrued a bit in Christianity. Adam was given dominion and authority over everything on the earth by God. When Adam sinned, he lost that authority. Isn’t that what the curse is describing? We are born into the world without authority. We are born of the fallen image of man. An orange can not come from an apple. Glorified man can not come from fallen man. That is why Jesus came. He lived His life, without His God powers, in obedience to the authority of the Father and reestablished the authority of man over the world and Satan.
Disobedience is the sin that separates us from God.