Does the Bible teach that believers are eternally secure?
Eternal security is really all about Jesus and His finished work—and that is permanent. The Gospel, after all, is good news that God has come to do what man can’t, bringing us back to Himself to experience eternal life with Him. Jesus lived the perfect life we can’t live and died the death we deserved to die, and by faith alone He offers each of us a trade, His righteousness for our sin. He became sin for us so that we might become the righteousness of God in Him (2 Corinthians 5:21). Jesus makes us new creations (2 Corinthians 5:17), a permanent work that can’t be undone. No one can snatch us out of God’s hand once He gives us eternal life (John 10:27-30), and nothing can separate us from His love (Romans 8:38-39).
The very idea of being able to lose salvation goes against the nature of the Gospel message. To lose salvation would be to undo Jesus’s finished work in saving us, cleansing us, making us new creations, adopting us, and uniting us as one with Himself. That can’t be done. For some passages that help us see the permanence of Christ’s work, we can look to 1 Corinthians 1:8 which says Jesus will sustain us to the end, blameless on the day He comes, and Hebrews 10:14 which establishes that Jesus not only forgave our past sins by His death on the cross but also did the work required to make us perfect.