Genesis 15:6 NLT  And Abram believed the Lord, and the Lord counted him as righteous because of his faith.

Clearly Paul is using Genesis 15:6 to prove that Abraham was justified by faith rather than works. But that interpretation, interestingly enough, was not the one held by the Jews of Paul’s day. The Jews by the time of Christ had begun to consistently interpret Abraham’s faith as a type of merit-earning faithfulness. In short, they saw Abraham’s faith in terms of good works.  

Paul knew that. Yet he deliberately chose Genesis 15:6 to prove just the opposite. That may seem strange to us, but Paul really couldn’t avoid that well-established understanding of the text. He needed to meet it head-on and demonstrate that, rightly interpreted, Genesis 15:6 confirmed his contention that Abraham had nothing to boast about because he had been justified by dependant faith apart from good works. The apostle proceeds to make his demonstration in Romans 4:4-8.  

Paul is fighting one of the most difficult battles ever waged. People don’t like to feel dependant on others for anything. We like to believe that we can take care of ourselves. As a result, we will do everything before giving up self-sufficiency. And yet in that surrender to our helplessness and God’s graceful powerfulness lies the secret of salvation.  

One of the keywords in Romans 4 is “credited”. The KJV translates the word as “counts” or “imputes”, while the RSV renders it as “reckon”. Paul uses the word 10 times in chapter 4 and five times alone in vs3-8. When employed in a financial or commercial context, it signifies putting something in somebody’s account  

Paul couldn’t make it plainer: God justifies sinful people not by what they have done, but through their faith and trust in Him. Their faith is counted as righteousness or imputed as righteousness. It is from this chapter that we get the phrase “imputed righteousness”. It is the work of a moment – the moment a person accepts God’s grace by faith the Lord credits their account in the books of heaven with Christ’s perfect righteousness. What happens when we come to Jesus? The Lord imputes to the believer the righteousness of Christ and pronounces him righteous (perfect) before the law and the universe. The Law’s requirement of perfection has been satisfied by our faith in Christ. That perfection is ‘imputed’ or ‘credited’ to us as a gift.