Abraham's faith was seen as righteous by God more than just Genesis 15:6
1) In Genesis 12 in obeying God in moving from his house, land and kindred, Abraham had an obedient faith (Hebrews 11:8). In Romans 4:13 Paul writes about "
righteousness of faith". Hence Abraham's faith in Gen 12 would be seen as righteousness by God.
2) Genesis 15:6 Abraham's faith was seen as righteous by God per Romans 4:3
3) Romans 4:19-22 Abraham's faith was seen as righteous by God (verse 22). Yet this context in Romans 4:19-22 does not refer to Genesis 15 but about 15 years later in Genesis 17-18 when Abraham was 100 years old.
4) Abrahams faith was seen as righteous by God when he offered Isaac, James 2:21
Abrahams being justified/righteous before God
was a process and not an one and done deal in Gen 15:6 no matter how Abraham lived his life. His being seen as righteous in Gen 15, and
continuing to be seen as righteous, was dependent upon his continued obedience through Gen 22 in offering Isaac. Had he disobeyed God in Gen 22 he would not continue to be seen as righteous/justified before God..
There is no indication that Abraham first had faith in Genesis 15:6 and was initially saved in Gen 15:6 by faith only.
--It is a fact Abraham already possessed an obedient faith prior to Gen 15:6 per Hebrews 11:8
--from resources I found on the internet, the verb "believe" in Gen 15:6 is perfect tense, so the idea in Gen 15:6 is that Abraham "kept on believing". His belief in Gen 15:6 therefore is a continuation of the righteous faith he already possessed in Gen 12 cf Hebrews 11:8.
The Form of the Hebrew Verb: The Hebrew construction strongly suggests that this was not the first time Abraham believed; rather, faith was Abraham’s characteristic response to God. The verb אמן (“to believe”) is a waw perfect (וְהֶאֱמִ֖ן) rather than a waw consecutive imperfect (ואמן). The waw consecutive imperfect is the normal form for past action. The independent perfect carries basically the same force. Moses had two options available to him to convey the simple past, “he believed.” He chose neither. This is what we would expect if Genesis 15:6 recorded Abraham’s first act of genuine faith. The independent imperfect and the waw perfect are often semantically equivalent and are used to convey modality, frequentativity, or futurity. The frequentative is the most likely meaning in this context. The idea would be something like, “And he kept on believing the Lord.” The grammatical evidence, then, suggests that this was not Abraham’s first act of faith, and consequently not the point of his justification. (See this document (Word | PDF) for supporting sources, esp. Carson, et al., NBC; Ross, BKC; Vickers, JBR; and Wenham, WBC.)
When Was Abraham Justified? | Part 1
--the claim Abraham was saved by 'faith only" in Gen 15:6 implies Abraham was a lost, unforgiven reprobate prior to Gen 15:6 but there is no evidence of this:
(a) Melchizedek king of Salem said Abraham was "of God" in Genesis 14:19.
(b) Genesis 15:1, God says of Abraham "
Fear not, Abram: I am thy shield, and thy exceeding great reward.". These are not words God would speak to an unforgiven, lost reprobate. Abraham must have already been in a saved/covenant relationship with God prior to Gen 15:6.
More from that above link:
Sources Supporting the Genesis 12 View
As confirmation to the above conclusion, it is nice to know that virtually all the commentators and theologians that I have come across who deal with the issue are in agreement that Abraham was justified by the events recorded at the beginning of Genesis 12. Luther, Calvin, Brakel, and Spurgeon defend a Genesis 12 justification, as do O. Palmer Robertson and Brian Vickers. (See this document [Word | PDF].)
Here are a few selections:
Luther:
Therefore if you should ask whether Abraham was righteous before this time, my answer is: He was righteous because he believed God. But here the Holy Spirit wanted to attest this expressly, since the promise deals with a spiritual Seed. He did so in order that you might conclude on the basis of a correct inference that those who accept this Seed, or those who believe in Christ, are righteous. (See this document [Word | PDF] for citation information and fuller context).
Calvin:
Therefore, by a consideration of the time in which this was said to Abram, we certainly gather, that the righteousness of works is not to be substituted for the righteousness of faith, in any such way, that one should perfect what the other has begun; but that holy men are only justified by faith, as long as they live in the world. . . . But now since after such great progress, he is still said to be justified by faith, it thence easily appears that the saints are justified freely even unto death. (See this document [Word | PDF] for citation information and fuller context).
Brakel:
Since justification is the fruit of faith when first exercised, justification is also the fruit when faith is exercised by renewal. This we observe for example in Abraham. Abraham was already a believer and had long before been justified prior to the promise in Genesis 15 being given to him, namely, “So shall thy seed be” (vs. 5). It is nevertheless stated in verse 6, “And he believed in the LORD; and He counted it to him for righteousness.” . . . Abraham was already justified prior to this; nevertheless, when subsequently he believed again, he was again justified. (See this document [Word | PDF] for citation information and fuller context).
Spurgeon:
I take it, beloved friends, that our text does not intend to teach us that Abram was not justified before this time. Faith always justifies whenever it exists, and as soon as it is exercised; its result follows immediately, and is not an aftergrowth needing months of delay. The moment a man truly trusts his God he is justified. Yet many are justified who do not know their happy condition; to whom as yet the blessing of justification has not been opened up in its excellency and abundance of privilege. (See this document [Word | PDF] for citation information and fuller context).
Robertson:
The fact that this declaration concerning the faith and resulting righteousness of Abraham comes at this particular juncture does not imply that now for the first time he believes and his faith is reckoned to him for righteousness. To the contrary, he continues in a state of faith and its resulting righteousness. But the placing of this declaration of righteousness at this juncture of the patriarch’s life underscores the fact that nothing has been added to faith as the way to righteousness. (See this document [Word | PDF] for citation information and fuller context).
Vickers:
When Paul chooses to include Abraham in Romans, he is not simply using a handy example that just happens to support his argument, nor does he merely use Genesis 15:6 as a proof text. While Genesis 15:6 is not, as we will see, the first time Abraham believed, and subsequently not the time of his, so to speak, conversion, it is a pivotal moment in the biblical narrative. (See this document [Word | PDF] for citation information and fuller context).
When Was Abraham Justified? | Part 1