What does the Bible say about losing salvation?

In Philippians 3:9-16, the Apostle Paul emphasizes that true salvation is a present reality for believers, grounded in the righteousness of Christ rather than their own actions. Paul highlights that salvation, from God's perspective, is complete and unchangeable, regardless of our experiences over time. When he speaks of pressing on, he's not suggesting that he may lose his salvation, but rather that he seeks to fully apprehend and enjoy the salvation that is already his through Christ. This encapsulates the doctrine of eternal security, affirming that once redeemed, a believer's salvation is assured by God's unchanging grace.