Existence of sin in the world

If heaven was a place of perfection, with no trace of sin, and Satan lived there with God and the other angels, where did Satan get the idea to rebel? And why did God allow it, knowing that it would cause so many to fall with him?

The Bible does not provide answers to those questions. Because God is all-powerful, he could have certainly prevented the fall of the angels and the subsequent fall of Adam and Eve. God does not explain why he did not prevent those falls—nor is he obligated to do so (Romans 11:33-36).

What we do know from the Bible is that God promised a Savior to crush the devil (Genesis 3:15), and Jesus Christ did exactly that (1 John 3:8).

Through Spirit-worked faith in Jesus Christ, Christians can confidently look forward to an eternal life of perfection with God (Revelation 21:3-4).