Is eternal life alone a sufficient guarantee to God that we will never sin again or turn and rebel against Him? If you think it is, then perhaps you should re-evaluate that line of thought.
Bear in mind that when Lucifer was created as an eternal spirit being, his creation was “perfect.” Ezekiel 28:15 says this about Lucifer: “You were perfect in your ways from the day you were created, Till iniquity was found in you.” Notice, he was perfect in all his ways. He was THE perfect created spirit being at that time–till iniquity was found in him, that is sin. In the course of time his mind became corrupted by sinful thoughts and desires, and he became Satan, the adversary and enemy of God.
Consider this–a perfectly created being turned in rebellion against his Maker and became God’s enemy, as it were. He attempted, unsuccessfully, to overthrow His Creator, and in the future, he will attempt to overthrow Him again, as Revelation 12:7-8 tells us: “And war broke out in heaven: Michael and his angels fought with the dragon [Satan the devil]; and the dragon and his angels [demons] fought, but they did not prevail, nor was a place found for them in heaven any longer.”
So the question is, how can God guarantee absolutely that this will not happen with us when we, as His born-again children, are changed to spirit and become God beings–“gods” (compare John 10:34-35)–in His divine Family?
Right now, we are flesh-and-blood human beings. Our physical existence is temporary and would remain so if there was no resurrection or change to immortal life. We are today begotten children of God who received God’s Spirit at baptism. We do not read that Satan was ever begotten by God’s Spirit when he was created. Rather, we read that God is reproducing Himself through man–not through angels. He begets us through His Holy Spirit and creates in us His divine nature. This potential to become true members in God’s Family–GOD beings–was never offered to angels (compare Hebrews 1:14; 2:5, 16; 2 Peter 1:2-4; Revelation 19:10; see also 1 Corinthians 6:3).
The guarantee that God wants to find in us is referred to in Philippians 2:5: “Let this mind be in you which was also in Christ Jesus.” In addition, we must consider Ephesians 3:14-19 in this context, stating:
“For this reason I bow my knees to the Father of our Lord Jesus Christ, from whom the whole family in heaven and earth is named, that He would grant you, according to the riches of His glory, to be strengthened with might through His Spirit in the inner man, that Christ may dwell in your hearts through faith; that you, being rooted and grounded in love, may be able to comprehend with all the saints what is the width and length and depth and height— to know the love of Christ which passes knowledge; that you may be filled with all the fullness of God.”
The mind that was in Christ Jesus was the mind of God the Father; and to become filled with the fullness of God–by growing in God’s grace and knowledge–is God’s absolute guarantee that we will never rebel against Him, because we will develop the same mindset that God and Christ have. This mindset says, in effect: “I will not sin; therefore, I cannot sin.”
God cannot rebel or sin against Himself. By creating in us His way of thinking through His Holy Spirit–His divine nature–He guarantees that we will NEVER sin or rebel against Him in the future.
We will become God beings; therefore, God the Father and Jesus Christ will not have to keep watching their backs in fear of their children and brothers and sisters rebelling in some manner. We will have developed and grown into the mindset of God. This necessitates, however, that we prove to God now that we are willing to develop His mindset. If God sees that we are unwilling to submit to Him and obey Him, then He will NOT grant us eternal life in His very Family.
But as long as we are willing to worship and please God, then our glorious future is guaranteed, and this will also be a guarantee to God that we will remain faithful to Him for all eternity.