-Jimmy Akin of Catholic Answers wrote an
article on the text of Genesis 15:6 as it relates to justification by faith and how he thinks the text should be applied in soteriological discussions. Each of his comments are cited in bold and are followed with a critique:
"Abraham is already a follower of God, someone who already has faith in him, and the context stresses Abraham’s good works and righteousness: (1) He defeated the evil kings. (2) He rescued Lot and the other captives. (3) He went to a priest of God and gave thanks for the victory. (4) He refused any reward from the wicked king of Sodom. (5) And so God himself promised to give Abraham a reward instead. (6) The fact that God is rewarding Abraham for what he has done shows this isn’t a case of a sinner coming to God and repenting so he can obtain forgiveness. It’s God rewarding a follower for faithful service. That means Abraham isn’t acquiring righteousness here for the first time. He is already righteous, as his actions have shown. Then Abraham believes the incredible promise that he will have a multitude of descendants, despite his age (cf. Rom. 4:19, Heb. 11:12), and God reckons that act of belief as a new act of righteousness on Abraham’s part."
None of the above comments really address the text of Genesis 15:6 on its own terms. The "it" is a reference to Abraham's faith. His faith is the basis for receiving righteousness. That belief does not preclude the obedience of Abraham. His trust in God and His promises was the instrumental cause of him being counted righteous, not any good works that he did.
"Some translations bring this aspect out better than others. The New American Bible does a particularly good job. It says that the Lord “attributed it to him as an act of righteousness.” Notice, by the way, that Abraham’s act of faith also wasn’t generic in nature. Abraham already believed in and trusted God in a general way. Here he is believing something very specific: that God will give him a multitude of descendants—a point Paul recognizes when he uses the verse (Rom. 4:17-22). And notice that the righteousness isn’t a counterfactual, purely legal thing. Instead, believing God when he tells you he will do something is a righteous act. Abraham did something actually righteous here."
There are translational differences. Many readings are legitimate. However, it is important to note that the addition of the word "act" is not present in the vast majority of translations. Moreover, it is absent from the Hebrew. The Hebrew word in Genesis 15:6 is "tsedaqah," which refers to justice or righteousness. It denotes a state of being righteous or just. It refers to what something is. The New English Translation has this footnote on Genesis 15:6:
"tn The sentence begins with vav (ו) plus a perfect verb. It does not show simple sequence, which would have been indicated with a vav plus preterite as in the surrounding clauses. The nuance may be that Abram had already come to believe or did so while God was speaking. For a detailed discussion of the vav plus perfect construction in Hebrew narrative, see R. Longacre, “Weqatal Forms in Biblical Hebrew Prose: A Discourse-modular Approach,” Biblical Hebrew and Discourse Linguistics, 50-98. The verb אָמַן (ʾaman) occurs with a Niphal and Hiphil opposition. In the Niphal it means “to be faithful, reliable, firm, enduring.” While in the Hiphil, the form used here, it means “to consider or treat something as reliable, or dependable.” Abram regarded God as reliable for this promise; he believed."
The Jewish Study Bible has this excerpt on Genesis 15:6:
"With nothing more
than an extravagant reiteration of
the promise of offspring, Abram
drops his question and trusts in
the LORD. "And thus you find,"
observes an ancient midrash about
this verse, "that our father Abraham inherited this world and the
world-to-come only as a reward
for the faith that he had" (Mek. of
Rabbi Ishmael, beshallab 7). In the
Tanakh, faith does not mean believing in spite of the evidence. It
means trusting profoundly in a
person, in this case the personal
God who has reiterated His promise."
Richard D. Phillips, in the book titled By Faith Alone, p. 81-82, expounds on Paul's usage of Genesis 15:6 in Romans 4:
"Paul is contrasting two approaches to righteousness. The one is secured by works and the other by faith. The one is based on merit ("his due") and the other on grace ("as a gift")...Most significant is Paul's contrast between something that is earned, so that it is credited to the person "as his due," verses something that is received by faith, which is received "as a gift." In other words, Paul says that Abraham received righteousness not as something he did but because of God's gracious gift. Carson explains: "Romans 4:4 establishes that there is a crediting, an imputing, that means something is credited to your account that you do not deserve." This means that "when faith is imputed to Abraham as righteousness, it is unmerited, it is all of grace, because it is nothing more than believing God and his gracious promise." Paul's whole argument here is that while Abraham's believing is correlated to his being credited with righteousness, this is not because he did something to earn it."
This line of reasoning employed by Jimmy Akin seems to reduce the promises made by God to Abraham to be something short of the gospel. Galatians 3:8, however, clearly says that gospel was announced to him in advance in seed form. Abraham looked forward to Jesus' day, and rejoiced (John 8:56-58).