What does Romans 4:16 mean?
Paul restates in this verse what he has said in the previous verses, but he describes it from the positive perspective. He has been talking about God's promises to Abraham and his descendants. He says once again that receiving the promised inheritance depends on faith, not on following the law. Because it is received by faith, the promise rests on God's grace. This is critical, since no human effort can secure this inheritance (Romans 3:23). Our own failures to follow God would make us ineligible for that righteousness (Romans 3:10). Salvation comes as a gift, and it is guaranteed to all of Abraham's offspring: offspring defined by faith, not by legalism.Paul has been careful to show that since Abraham was declared righteous by God for believing God, everyone who comes to God by faith is Abraham's offspring. This includes both Jews and Gentiles who believe in God. In that way, Abraham is the father of all believers.
Romans 4:13–25 continues to focus on the faith of Abraham. God made promises to Abraham and his descendants, promises which Abraham believed. Those promises can't be received by keeping the law, but only by faith. God promised Abraham a son with Sarah, and Abraham continued to believe that promise would be kept even as it became less and less likely in human terms. We, too, can be counted as righteous by faith in Jesus' death for our sins and God's resurrection of Him for our justification.
Romans 4 is all about the faith of Abraham. God declared Abraham righteous because of his faith, not because of his works. A declaration of righteousness was God's gift, not a payment. This righteousness is available to everyone, circumcised or not. God declared Abraham righteous many years before he was circumcised, making him the spiritual father of all who believe, whether circumcised or not, whether Jew or Gentile. God's promises to Abraham and his offspring can't be received by keeping the law, only by faith. Abraham's faith in God's promise of a son with Sarah did not waver even as he grew older. God will declare us righteous, as well, if by faith we believe in the God who delivered Jesus to die for our sins and raised Him back to life for our justification.