There is only one passage in Scripture where Lucifer is mentioned and the answer to your question is there. In Isaiah 14:12-15 we read: “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 also sit on the mount of the congregation on the farthest sides of the north; I will ascend above the heights of the clouds, I will be like the Most High.’ Yet you shall be brought down to Sheol, to the lowest depths of the Pit.” It is clear that Lucifer REBELLED AGAINST HIS CREATOR. He wanted to “ascend into heaven” and exalt his throne “ABOVE the stars of God” (verse 13). Verse 14 goes even further and says, “I will be like the Most High” which means “he wanted to DETHRONE GOD and take His place as God. We read in 1 Samuel 15:23, “For REBELLION is as the SIN of witchcraft.” This is the horrible sin that Lucifer harbored in his heart.

But there is another passage that really brings out the “root SIN” that led to the “sin of rebellion.” I’m speaking of Ezekiel 28:12-15 where it seems obvious that God is speaking to Lucifer (even though his name is not mentioned). That passage says, “Thus says the Lord GOD: ‘You were the seal of PERFECTION, full of WISDOM and PERFECT IN BEAUTY. You were in Eden, the garden of God; Every precious stone was your covering: The sardius, topaz, and diamond, Beryl, onyx, and jasper, sapphire, turquoise, and emerald with gold. The workmanship of your timbrels and pipes was prepared for you on the day you were created. You were the ANOINTED CHERUB who covers; I established you; You were on the holy mountain of God; You walked back and forth in the midst of fiery stones. YOU WERE PERFECT IN YOUR WAYS from the day you were created, TILL INIQUITY WAS FOUND IN YOU.” Lucifer was created by God in perfection! He was “full of wisdom” and “perfect in beauty.” He was “the anointed cherub who covers” which means that God gave him, as the highest of all angels, the mission of “protecting His throne in heaven.” Yet sadly his heart was “filled with PRIDE” because of his wisdom, beauty, and the high place in heaven that God had given to him. Instead of “protecting the throne” from another angel that may seek to rebel against God, he himself became the rebel! He had been “perfect in all his ways” but then “iniquity was found in him.” The sin of PRIDE began in his heart and as it was nurtured, the sin of REBELLION took root. This rebellion, at some point, caused him to openly defy God and we learn from Scripture that many angels followed him in his rebellion against God. And thus we read of “the devil and his angels” in Matthew 25:41. In Matthew 12:24 he is called “Beelzebub, the RULER OF THE DEMONS.”

We also know that it was the devil who tempted the woman in the Garden of Eden to eat of the forbidden fruit (see Genesis 6:1-5 with 2 Corinthians 11:3 and Revelation 20:2) and it is quite instructive to see that he used “the sin of PRIDE” in his temptation. He told the woman, “You will not surely die. For God knows that in the day you eat of it your eyes will be opened, and YOU WILL BE LIKE GOD, knowing good and evil” (verse 5). The very sin that brought about his fall was used against her, for he wanted to plant the “seed of pride in her heart” and the “desire to be like God.” Sadly, his temptation worked, for she succumbed to the temptation and ate of the forbidden fruit and then gave it to her husband (Adam) and “he ate” (verse 6). Ever since then the devil has been using that same strategy against mankind, for he wants men and women to be PROUD and in doing so to REBEL against God. Thousands of years after the fall in the Garden of Eden we read of this in 1 Timothy 3:6, “not a novice, lest being PUFFED UP WITH PRIDE he fall into the same condemnation AS THE DEVIL.” The subject in that chapter is qualifications for men bearing oversight in a local church and the warning is sounded that they must not be a NOVICE (a new, inexperienced Christian) or they may become PROUD and desire, like Lucifer did, a high position for which he is not qualified. The “sin of pride” is the original sin of the universe, and the devil is seeking to gain the hearts of humans with this same sin and join him in his rebellion against God.  (DO)  (656.3)