Paul shows by the example of Abraham that faith justifies, and not the law or the works of the law.

4 What shall we say then that Abraham, our father as to the flesh, did find? ² If Abraham were justified by deeds, then he has wherein to glory, but not with God. ³ For what does the scripture say? Abraham believed God, and it was counted to him for righteousness. ⁴ To him who works, the reward is not reckoned from favour, but as his due. ⁵ To him who does not work, but believes on him who justifies the ungodly, his faith is counted for righteousness. ⁶ It is just as David describes the blessedfulness of the person to whom God ascribes righteousness apart from deeds: ⁷ Blessed are those whose unrighteousnesses are forgiven, and whose sins are covered; ⁸ blessed is that man to whom the Lord does not impute sin.

⁹ Did this blessedness come then upon the circumcised, or upon the uncircumcised? We say that faith was reckoned to Abraham for righteousness. ¹⁰ How then was it reckoned? In the time of circumcision, or in the time before he was circumcised? Not in the time of circumcision, but when he was yet uncircumcised.

¹¹ And he received the sign of circumcision as a seal of the righteousness that is by faith. This faith he had when still uncircumcised, to the intent that he should be the father of all who believe, though they are not circumcised, so that righteousness may be ascribed to them also; ¹² and to the intent that he should be the father of the circumcised, not only because they are circumcised, but because they walk also in the steps of that faith that was in our father Abraham before the time of circumcision.

¹³ For the promise that he would be the heir of the world was not given to Abraham or to his seed through the law, but through the righteousness that comes by faith. ¹⁴ For if those who are of the law are the heirs, then faith is but vain, and the promise of no effect. ¹⁵ Because the law causes wrath.

But where no law is, there is no transgression. ¹⁶ Therefore it is by faith that the inheritance is given, so that it may come by favour, and so the promise may 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. ¹⁷ As it is written: I have made you a father to many nations, even before God whom you have believed, who gives life to the dead, and calls those things which are not, as though they were.

¹⁸ This Abraham, contrary to hope, believed in hope that he would be the father of many nations, according to that which was spoken: Thus shall your seed be. ¹⁹ And he fainted not in the faith, nor yet considered his own body (which was now dead inasmuch as he was almost a hundred years old), nor yet that Sarah was past childbearing. ²⁰ He staggered not at the promise of God through unbelief, but was made strong in the faith and gave honour to God, ²¹ fully persuaded that what he had promised, that he was able to make good. ²² And therefore it was reckoned to him for righteousness.

²³ It is not written for him only that faith was reckoned to him for righteousness, ²⁴ but also for us, to whom it will be credited as righteousness if we believe on him who raised up Jesus our Lord from death, ²⁵ who was delivered for our sins, and rose up again to justify us.