What does Romans 4:21 mean?
Paul defines Abraham's faith in a very helpful way in this verse. Abraham was "fully convinced" God was able to do as He promised. He remained fully convinced even as the years passed without the promise being fulfilled. Abraham never doubted God could keep His word even through his own "as good as dead" (Romans 4:19) body. In fact, the more time that passed, the stronger Abraham's faith became. This, of course, was based on Abraham's experiences with God, which proved that God was trustworthy.Paul has shown that all of us come to God—that we are declared righteous by Him—only through this very same faith that Abraham had. God calls us to be "fully convinced" that, in Christ, our sins are forgiven and we are welcomed into God's family. It is this "trust" which saves us from our sins (Hebrews 12:1–2), not good works or legalism.