Why did God give the law of Moses? One reason was to teach the lesson that we proud sinners need to hear most: We cannot rescue ourselves. Even with the best legal system, devised by God Himself, we cannot save ourselves. We need the Savior! Yes, God saves us by His own sheer kindness or “grace,” which we can never earn or deserve (2 Timothy 1:9; Titus 3:5). Our part is to depend on Him for everything. This dependence Paul calls “faith.” The system of dependence is often called “the faith.” Paul repeatedly draws a sharp distinction between saving “faith” and futile “works” (Romans 9:32; Ephesians 2:8-9).
When God sees faith, that “faith is counted to him as righteousness” (Romans 4:3; like Romans 4:6, 9, 10, 11, 22-24. In other words, when God sees that we depend on Him, He credits that—He counts that—as if it were real righteousness. He knows how sinful and unworthy we are. Yet He makes the decision that He alone can make. As the only Lawgiver and Judge, He pronounces us, “Not guilty!” How can God be perfectly just, yet treat us as innocent, even “righteous,” in His eyes? The answer is that the demands of justice have already been met. All the punishment we deserved was heaped onto God’s Son (Isaiah 3:5-6; 1 Peter 2:24). He paid the full penalty for our sins when He suffered and died on the cross. Justice was fully served, and God feels free to transfer His own righteousness to us (2 Corinthians 5:21) (For more on the source of salvation, see Study Note Five)
God’s basis for saving us is His Son’s life and death. God’s means by which we receive all this grace is the dependence He calls “faith.”
But the words “it was counted to him” were not written for his sake alone, but for ours also. It will be counted to us who believe in Him who raised from the dead Jesus our Lord, who was delivered up for our trespasses and raised for our justification (Romans 4:23-25).
Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ (Romans 5:1).