How do we know salvation is through grace alone?

The doctrine of salvation by grace alone, or 'sola gratia', is clearly articulated in several passages of Scripture. For instance, Ephesians 2:8-9 states, 'For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast.' This scripture emphasizes that human effort cannot contribute to our salvation; it is purely a gift from God. Furthermore, throughout the Bible, the theme of grace is depicted as the unmerited favor of God toward sinners, primarily manifesting in the sacrificial death of Christ. The prophets of the Old Testament and the apostles of the New Testament continually reinforce this message, encouraging believers to rest in the finished work of Christ rather than their own deeds.