v1: Abraham, and David, knew the truth of justification by faith. So Paul uses the OT to demonstrate that, in a sense, the gospel is not new.

v2: As in 3.27, the doctrine of justification by faith gives no room for boasting.

v3: "Abraham believed God," is the clear basis of his salvation; through his faith, righteousness was credited (or accounted, or imputed) to him; Gen 15.4-5. The sinner is therefore accounted as righteous, and nothing can change that back.

v4: The doctrine of justification by faith gives no room for works; this is different from the concept of working for wages; the receipt of wages is an obligation on the part of the employer, not a gift.

v5: God justifies the wicked, not because He condones sin, or is complacent towards sin, but simply because a person puts his faith in Jesus Christ. There is no other way for a person to be made righteous, however wicked he was before. The gospel is rightly called a scandal, since God should choose to justify the wicked; what glorious scandal this! Paul is clear that we are justified apart from our works.

v6: The testimony of David adds to that of Abraham; his words speak of righteousness apart from works. The reader recalls that David committed adultery and murder; his confession of Ps 51 is followed by his joy in Ps 32.

v7: Justification involves the covering of all sins and transgressions, the things we do wrong, and our falling short of God's standards. All this is dealt with; no wonder David says, "Blessed!"

v8: God does not impute sin to anyone; by nature we have sin, and are subject to condemnation. The glory is that our imputed righteousness answers all personal sins.

v9: Paul brings in and addresses the question of circumcision, and its place in the justification. He begins be considering Abraham's experience, for he is "our forefather," which is true of Jews and Gentiles (Gal 3.9).

v10-11: The key question is whether Abraham was justified before he was circumcised, and therefore that circumcision was a sign of his faith; or whether he was justified after he was circumcised, and then it could be argued that circumcision was necessary for justification.

The scripture is clear; Abraham believed God and was justified BEFORE he was circumcised Gen 15.4-5; 17.24, a gap of at least 13 years, see Gen 16.16. Circumcision was therefore a sign, a "seal" of what had happened, just as baptism is a sign of our faith in Christ. For us the Holy Spirit is our seal (Eph 1.13). Thus, even for Jews, circumcision was never a condition of righteousness. Abraham is therefore the father of all who believe, see Gal 3.9.

v12: The call to believing Jews, Col 4.11; faith is more than circumcision; and it is expected that those who believe also "walk in the footsteps" of Abraham, in living by faith.

v13-15: The promises to Abraham, Gen 15.5; 17.5; Gal 5.23, 28, 31; not through the law but through faith. The Jews who depended on the law, and on their obedience to the law, therefore missed out on this promise. (There were of course promises to those who obeyed the law.) But the law could not bring them to inherit those promises made to Abraham on the basis of his faith.

And, since we cannot keep the law, we find that it brings wrath, not salvation and righteousness.

v16-17: The reality of God's promises and the power of faith; by faith the promise is fulfilled. For Abraham, the impossible was achieved; God called something which was not, in bringing forth Isaac; He made the world from nothing (Heb 11.3); He gives life to the dead, in the birth of Isaac; Abraham was "already dead" (v19), and Sarah's womb was also dead.

v18: "Against all hope," or 'contrary to hope;' even though the thing promised was impossible, Abraham believed God; faith joins human impotence with divine omnipotence, and the impossible becomes real. Abraham not only produced a son, but he became the "father of many nations."

v19: Abraham faced the facts that shouted out "impossible;" and in the face of them, he clung to God's promises, confident in God's power and faithfulness; what He had said would come to pass.

v20: Some waver in their unbelief; but Abraham was strengthened in his faith, through which God is glorified. In the first verses of chapter 5, Paul teaches that we too glorify God through our faith in Him.

v21: Abraham was utterly convinced, "fully persuaded;" God had spoken and nothing could change that. The link between God's truth and His power; He declares nothing that He cannot perform. Our faith grasps that link, and trusts in it.

v25: Horatius Bonar says; "It was because the justifying work was finished that resurrection was possible." (The Everlasting Righteousness, p 419.)