Gospel Guidebook: Getting and Keeping It Right 
Romans 4:17-22 and the Demonstration of Abraham's Faith
In my studies on Romans 4, I have heard two people (one a New Perspective on Paul theologian and the other an Eastern Orthodoxy apologist) argue that Romans 4, especially verses 17-22, was meant to show the process of Abraham's justification over a period of many years. According to these two individuals, Abraham was not justified by a singular act of faith, as recorded in Genesis 15:6 and quoted by Paul in Romans 4:3, but was justified as he lived out his faith.
In this short article, I will show that the Apostles Paul and James carefully wrote their letters in a manner that dispels this notion that Abraham was justified over a period of time, as opposed to a moment of time.
In Romans 4:17-22, Paul is not referring to Abraham's justification-by-faith (imputed righteousness) moment in Genesis 15:6, nor is he referring to Abraham's justification as an ongoing process that spanned from at least Genesis 15:6 (when he was probably between 75 and 85 years old) to Genesis 21:5 (when he was about 100 years old). Rather, he is referring to a subsequent demonstration of faith in Genesis 17:5 (which was when he was about 100 years old, cf. Genesis 17:17 and Genesis 21:5) that represented (vindicated) the justification-by-faith that Abraham already experienced in Genesis 15:6.
In James 2:21-23, James did something similar, but instead of referring to a subsequent demonstration of faith, he refers to a subsequent demonstration of works-empowered faith in Genesis 22:9-12 that represented (vindicated) the justification-by-faith that Abraham already had.
Neither of these subsequent events referred to by Paul and James contributed to or added to Abraham's justification-by-faith in Genesis 15:6. Likewise, the lack of these subsequent events would not have canceled or impaired Abraham's justification-by-faith in Genesis 15:6. These subsequent events enabled Abraham to experientially demonstrate (vindicate) his previous justification-by-faith moment, thereby bringing glory to both God and himself.
Both James and Paul express that they are referring to these subsequent events as representative (vindicating) events of Abraham's justification-by-faith moment by referring back to Genesis 15:6 with the qualifying expressions "And the Scripture was fulfilled" (James 2:23a) and "And therefore" (Romans 4:22a). These two statements prove that Abraham's justification in Genesis 15:6 was not part of a process. It was a singular event. Again, it is important to see how both James and Paul refer back to Genesis 15:6 and speak of his past justification (i.e., "was imputed for righteousness," being in the aorist tense).
Furthermore, in James 2:23, James tells us that this subsequent event of justification by works in Genesis 22 gained Abraham the honor of being called "the Friend of God" (James 2:23c, cf. 2 Chronicles 20:7, Isaiah 41:8). James enumerates these two separate events using the Greek correlative conjunctions kai ... kai (both ... and) (i.e, [1]"Both the Scripture was fulfilled ... [2] and he was called the friend of God."). Paul Miles (PhD from Tyndale Theological Seminary and Executive Director of Grace Abroad Ministries) comments on this by saying, "The Scripture that was fulfilled is Genesis 15:6, which speaks of his justification (being called, 'righteous') by God and the second thing that happened is that he was called, 'a friend of God,' that is, he was justified (called, 'righteous') by men. The first justification is why he is in heaven today and the second justification is why he is still hailed as a hero of the faith today (Heb 11:17–19)." (Does James Make Works a Criterion for Eternal Life?). In James 2:24, James further emphasizes this by stating that these two events referred to two different types of justification, one by works and one by faith. (For details on James 2:24, see my article Even More Objections Answered regarding Romans 4 or Paul Miles' paper mentioned above.)
The story of Abraham's heroic demonstration of faith in Romans 4:17-22 is inspiring, informative, and descriptive, and it shows us the amazing extent to which faith can go. I believe that the Apostle Paul included this passage of Scripture to encourage us (and possibly to persuade some fence sitters in Rome) to believe, even against all odds, because by believing in him that raised up Jesus our Lord from the dead, we too could have righteousness imputed to us, just like Abraham did (Romans 4:24). It is striking to note that just two verses later in Romans 5:1, Paul describes the situation of believers as "being justified by faith" (aorist past tense participle) and as having peace with God through our Lord Jesus Christ (present indicative). This is worth repeating. Please note that these believers were not in the process of being justified, they were justified (past tense) and as a result currently enjoying peace with God God through our Lord Jesus Christ (present tense). Likewise, we who have believed in Jesus Christ for eternal life (John 3:16) can rest assured that we were imputed with righteousness the moment we believed.