The belief that the devil is salvageable and can be saved has been around for a long time. Origen (c. 185 to c. 253 A.D.), for example, taught that God will ultimately save all humans, a belief known as universalism. He also supported the teaching that Satan would someday be reconciled to God.
Lucifer, prior to becoming the devil, was a righteous angel created to serve at God's throne (Ezekiel 28:14). After rewarded with his own throne (Isaiah 14:13) he rebelled, attacked heaven (verses 12 - 15) and became God's chief enemy. Does the Bible, however, indicate that since these events the devil has softened his heart? Has he shown any possibility that he might reconsider his rebellion and allow himself to be saved?
The direct words from the devil are recorded in only four Scriptural places. They are Genesis 3:1 - 5, Job 1:6 - 12, 2:1 - 7 and Matthew 4:1 - 11. The adversary also inspired Peter's words that rebuked Christ for planning to suffer and die for humanity (Matthew 16:22 - 23).
Satan, in each of the above examples, showed no signs of remorse for his sins. He showed not one iota of mercy or pity, but rather zealously worked to thwart both God and man.
The devil, in Genesis, deceived Eve into sinning by taking advantage of her lack of character. His actions led to God's judgment upon humanity (Genesis 3:16 - 19). In Job, He showed his contempt for the Eternal when he accused him of having to buy the patriarch's love and obedience.
Does Job fear God for nothing? Have You not made a hedge around him, and around his house . . . You have blessed the work of his hands . . . but put forth Your hand now, and touch all that he has, and he will curse You to Your face (Job 1:9 - 11, HBFV).
When the devil was allowed direct access to Jesus for forty days, he did nothing but tempt him to sin (Luke 4:1 - 13)! His preoccupation with destroying everything he can has even lead him to whining about humanity's sins 24 hours a day in heaven (Revelation 12:10)!
The Bible predicts Satan will soon deceive and rule the world through the Beast and False Prophet. His goal is to be the permanent ruler of earth and be worshipped as a god. He is predicted to gather a great army whose sole purpose is to repel a returning Christ so that he can continue his authoritarian rule over humans (Revelation 19:11 - 21).
The efforts of the devil will fail, however, and he will be put in a spiritual prison for 1,000 years (Revelation 20:1 - 3). After his release, he is prophesied to gather yet another human army whose goal this time will be to remove Jesus' active rule over the earth. This plan, like the one before it, will also fail (verses 7 - 9).
How can God know with certainty that the devil will do evil in the near future? How does this knowledge affect Satan being saved?
The rebellion of the devil, against God, was so great that it caused the first, and one of the rarest, events to occur in the universe!
Lucifer's negative thoughts against his Creator were so strong and repetitive that they eventually sealed himself evil! He made himself as perfectly dedicated to do wrong as God is to doing right. He sealed his character by himself, unlike Christians who must be sealed righteous by the Eternal, in the resurrection, in order to receive eternal life (Matthew 5:48, John 17:23, Ephesians 4:13, Hebrews 11:40, 12:23).
Since his rebellion, the devil has never shown the slightest remorse for any of the pain and suffering he has caused. There is not a single Biblical example of him showing a "softer side" or even hinting that he would be willing to repent which would lead to being saved.
God knows what the devil will do in the future because his evil character is unchangeable and permanent. Satan, in spite of knowing all his plans will utterly fail, is incapable of changing his course. He has locked himself into a state of mind that cannot be saved!
The Final Irony
The purpose of the lake of fire is to destroy (not torture!), for all eternity, any human, demon or state of existence thrown in it (Luke 4:33 - 34, Revelation 20:14 - 15). The destiny of the devil is to be tossed into this lake (Revelation 20:10) to receive the ultimate penalty.
I will bring you (Satan the devil) to ASHES upon the earth, before the eyes of all who see you. All who know you among the people shall be astonished at you; you became a terror, and YOU WILL NOT BE ANY MORE (Ezekiel 28:18 - 19, HBFV).
Ironically, the lake of fire is God's way of saving the devil but not how most would think. His last merciful act toward his hardened enemy will be to save him from eternally torturing himself by ending his existence.