How do we know that salvation is by faith alone?

The doctrine of salvation by faith alone is rooted in biblical teachings such as Ephesians 2:8-9, which states, 'For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.' This passage affirms that salvation is a divine gift, highlighting that human effort cannot attain righteousness before God. Furthermore, the emphasis on faith alone upholds that true faith is fully reliant on Jesus Christ and His finished work. Therefore, it clarifies that salvation is an act of God's grace rather than human merit.