Patristic Wisdom: Looking to the Second Sunday in Lent

What then shall we say that Abraham our father has found according to the flesh? For if Abraham was justified by works, he has something to boast about, but not before God. For what does the Scripture say? “Abraham believed God, and it was accounted to him for righteousness.” Now to him who works, the wages are not counted as grace but as debt.… For the promise that he would be the heir of the world was not to Abraham or to his seed through the law, but through the righteousness of faith. For if those who are of the law are heirs, faith is made void and the promise made of no effect, because the law brings about wrath; for where there is no law there is no transgression. Therefore it is of faith that it might be according to grace, so that the promise might be sure to all the seed, not only to those who are of the law, but also to those who are of the faith of Abraham, who is the father of us all (as it is written, “I have made you a father of many nations”) in the presence of Him whom he believed—God, who gives life to the dead and calls those things which do not exist as though they did. (Romans 4:1–4, 13–17)

Paul confirms by quoting the law that Abraham is the father of all who believe, and so the promise is firm if they abandon the law on account of their faith, because the promise of the kingdom of heaven is given to the righteous, not to sinners. Those who are under the law are under sin, because all have sinned, and it is not possible for anyone who is under to law to receive grace, as he says to the Galatians: You are severed from Christ, you who would be justified by the law; you have fallen away from grace.

In order to teach that there is one God for all, Paul tells the Gentiles that Abraham believed in God Himself and was justified in His sight. The Gentiles also believe in Him, that they may be justified, and so there is no difference between Jew and Greek in faith, for when the circumcision and the uncircumcision are taken away they are made one in Christ, because Abraham also believed when he was still uncircumcised and was justified.

Having said this, Paul invites the Gentiles to share the faith of Abraham, who believed God while he was still uncircumcised. Now that that faith is preached in Christ, he has been raised from the dead, along with his wife. For when they were already very old they sprang back to life, so that Abraham did not doubt that he would have a son by Sarah, whom he knew to be sterile, and who had long since ceased to have her menstrual period. Paul said this so that they would not worry about circumcision or uncircumcision, but that they would respond eagerly because of their faith, secure in the knowledge that the one in whom they believe is no other than the one who gives life to the dead, and that when he wants to bring things which do not exist into being, they appear immediately by his mere will.

Ambrosiaster, Commentary on Romans 4.17