How do we know that salvation is only by grace through faith?

Salvation by grace through faith is a foundational doctrine in Reformed theology, rooted in Ephesians 2:8-9, which declares that it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God. This truth is reinforced throughout Scripture, where we learn that our works cannot earn salvation or appeal to God, as all have sinned (Romans 3:23). Only by God's sovereign choice and mercy do we receive salvation through Christ's atoning work. It is this grace that assures believers of their standing before God, unmerited and without condemnation.