Romans 4:16-17, “16 That is why it depends on faith, in order that the promise may rest on grace and be guaranteed to all his offspring—not only to the adherent of the law but also to the one who shares the faith of Abraham, who is the father of us all, 17 as it is written, “I have made you the father of many nations”—in the presence of the God in whom he believed, who gives life to the dead and calls into existence the things that do not exist.”
We are fallen, and cannot keep the law of God perfectly; therefore, only the work of the incarnate Son of God, Jesus Christ, can provide what we need to be declared righteous before Him. Divine grace alone can save us, grace that is sufficient for our justification and not mixed with our obedience to the Lord. The only means of justification consistent with grace is the faith that brings nothing to the table, not even faith-motivated good deeds. Justifying faith says: “Lord, all I deserve is your judgment. Even with your help, I cannot do enough good to meet your perfect standard. All that avails for me is the righteousness of Christ. Please, clothe me with it” (see Rom. 4:1–16a). Such faith is the gift of God to His people: “For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast” (Eph. 2:8–9).
Those with such faith are Abraham’s true offspring, which includes Jewish believers in Jesus (“the adherents of the law”) and “the one who shares the faith of Abraham,” as Romans 4:16b teaches. Paul picks up on a theme to which he has already alluded and to which he will return in future chapters of Romans, namely, that the true Jew—the actual citizen of God’s kingdom—is not merely Jewish outwardly but has authentic faith in the Lord (2:29; 9:6–8). Jewish believers in Christ have the privilege of being from the genetic stock that produced our Lord’s human nature. However, they have no special status as sons. Jewish and Gentile Christians alike are children of Abraham—and thus of God (Gal. 3:26–29).
Romans 4:17 begins to look at the nature of Abraham’s faith, revealing to us what he believed. Simply put, Abraham believed God, meaning that the patriarch trusted that the Lord would do what He promised. Abraham did not just believe in God and tip his hat to the Creator’s existence. Instead, Abraham had the kind of faith that takes the Lord at His word. He trusted God when He said, “I have made you the father of many nations.” God spoke these words from Genesis 17:5 before Isaac was conceived, which is important because it indicates that Abraham trusted that what God had said was as good as done even though the promise had not yet been fulfilled in the birth of Isaac. Abraham was assured that God would make him the father of many nations; he believed that the same God who created all things out of nothing (“called into existence the things that do not exist”; Rom. 4:17) would do the same for him and give him a son even though Sarah was barren.
Dr. R.C. Sproul has often noted that it is not enough merely to believe in God. We must also believe God, which means that we believe not only that He exists and can do what He says but that He will do what He says. This is the kind of faith that pleases God. Justifying faith believes that God will do what He says and declare us righteous in Christ. It thus carries with it a degree of assurance that His promises are true and reliable.