The original sin of Lucifer is described in Isaiah 14:12-15, which says, '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! 13 For you have said in your heart: 'I will ascend into heaven, I will exalt my throne above the stars of God; I will also sit on the mount of the congregation on the farthest sides of the north; 14 I will ascend above the heights of the clouds,
I will be like the Most High.' 15 Yet you shall be brought down to Sheol, to the lowest depths of the Pit.'
Paul alluded to this sin when he wrote that an elder must
not be 'a novice, lest being puffed up with pride he fall into the same condemnation as the devil' (1 Timothy 3:6).
The question as to when this took place is not clear. Some say it was before the creation. We tend to believe it happened after man had been created, perhaps in connection with Satan's temptation of Eve. But we are not dogmatic on this point.