2 For if Abraham was justified by works, he has something to boast about, but not before God. 3 For what does the Scripture say? “Abraham believed God, and it was counted to him as righteousness.” 4 Now to the one who works, his wages are not counted as a gift but as his due. 5 And to the one who does not work but believes in him who justifies the ungodly, his faith is counted as righteousness, 6 just as David also speaks of the blessing of the one to whom God counts righteousness apart from works:John Piper does a fine job of critiquing non-imputational interpretations of this passage: “When Paul begins to explain in verse 4 what he means by ‘counted to him as righteousness’ in verse 3, he talks about it in terms of something external (a wage) being credited to our account, rather than something internal (faith) being treated as righteousness.” This righteousness then is not something we already possess, nor is it in us.
On the contrary, it is foreign, or alien to us. God credits the righteousness of Christ towards us when we trust Christ. This is significant because it helps define Paul’s use of the term “faith”. As Piper writes later, “Justification in Paul’s mind is God’s imputing righteousness to us ‘by faith’ rather than faith being treated as righteousness within us.”