How do we know that salvation comes by grace alone?

The doctrine of salvation by grace alone is rooted in the belief that God takes the initiative to save us. Ephesians 2:8-9 affirms that we are saved by grace through faith, and that not of ourselves; it is the gift of God, not of works, so that no one may boast. This truth is crucial for understanding that our works cannot merit salvation; it is solely based on God's mercy and love. The historical example of Abraham and Isaac further illustrates that we are children of promise, not of our own striving, but of God's sovereign grace.