But you're not reading the whole thing. James clearly points out that Abraham believed God and it was reckoned to him as righteousness.
[Jas 2:23 KJV] And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
James is saying that the faith scripture (Abraham believed God and IT--Abraham's belief--was imputed unto him for righteousness) is fulfilled in Abraham's willingness to sacrifice Isaac.
You should start at verse 14, instead of verse 23. It gives you the full context of what James is talking about:
What does it profit, my brethren, if someone says he has faith but does not have works? Can faith save him? If a brother or sister is naked and destitute of daily food, and one of you says to them, “Depart in peace, be warmed and filled,” but you do not give them the things which are needed for the body, what does it profit? Thus also faith by itself, if it does not have works, is dead. But someone will say, “You have faith, and I have works.” Show me your faith without your works, and I will show you my faith by my works. You believe that there is one God. You do well. Even the demons believe—and tremble! But do you want to know, O foolish man, that faith without works is dead? Was not Abraham our father justified by works when he offered Isaac his son on the altar? Do you see that faith was working together with his works, and by works faith was made perfect? And the Scripture was fulfilled which says, “Abraham believed God, and it was accounted to him for righteousness.” And he was called the friend of God. You see then that a man is justified by works, and not by faith only. Likewise, was not Rahab the harlot also justified by works when she received the messengers and sent them out another way? For as the body without the spirit is dead, so faith without works is dead also.

Bible Gateway passage: James 2:14-26 - New King James Version
Faith Without Works Is Dead - What does it profit, my brethren, if someone says he has faith but does not have works? Can faith save him? If a brother or sister is naked and destitute of daily food, and one of you says to them, “Depart in peace, be warmed and filled,” but you do not give them...
James is not talking about works after one is saved.
He's talking about works in addition to faith being required to save..
"Can faith save him [if he does not have works]?
James then gives an example of having faith, but not DOing, and raises the question: "what does it profit"?
NOTHING! It profits you nothing!
And that's true for both the dispensation of grace and for the dispensation of the Kingdom. But it's ESPECIALLY true for the Kingdom gospel, because works have value within it, while under grace, you "have reason to boast, but not before God!"
James says "show me your faith without your works, and I will show you my faith by my works. . . . faith without works is dead!" In other words, the answer to the question he asked in verse 14, is "faith without works is dead! It cannot save!"
James brings up demons, saying even they believe, pointing out that if you just believe, there's no difference between your faith and theirs!
The literal translation in verse 20 is "faith apart from works is worthless"! It has no value!
James then asks "was not Abraham our father justified by works when he offered his son Isaac on the altar? Do you see that faith was working together with his works, and by works faith was made perfect?" Verse 23: And the scripture was fulfilled which says, "Abraham believed God, and it was accounted to him for righteousness." And he was callled the friend of God. (24) You see then that a man iis justified by works, and not by faith only."
Notice that in verse 23, James is quoting from Genesis 15 (verse 6, specifically), talking about works, yet if you go and read the rest of Genesis 15, Abraham didn't actually do ANYTHING!
In fact, he COULDN'T do anything! He was asleep!
Genesis 15 is the chapter where God cut a covenant (literally where we get the phrase "to cut a deal") with Abram (which is something else to consider, that God had not yet renamed him to "Abraham" in Genesis 15) where He alone (and not with Abram) walked through the middle of the animals which Abram had cut in half.
It wasn't until Genesis 17 where God required something of Abraham, that being, circumcision, a work of the flesh if there ever was one! James alwo mentions Rahab, pointing out her sending the messengers out a different way to protect them, calling that "works."
He then ends the thought with "for as the body without the spirit is dead, so faith without works is dead also."
The entire passage is about how works are required in order for one's faith to be valid.
Now let's contrast that with what Paul wrote:
But now the righteousness of God apart from the law is revealed, being witnessed by the Law and the Prophets, even the righteousness of God, through faith in Jesus Christ, to all and on all who believe. For there is no difference; for all have sinned and fall short of the glory of God, being justified freely by His grace through the redemption that is in Christ Jesus, whom God set forth as a propitiation by His blood, through faith, to demonstrate His righteousness, because in His forbearance God had passed over the sins that were previously committed, to demonstrate at the present time His righteousness, that He might be just and the justifier of the one who has faith in Jesus. Where is boasting then? It is excluded. By what law? Of works? No, but by the law of faith. Therefore we conclude that a man is justified by faith apart from the deeds of the law. Or is He the God of the Jews only? Is He not also the God of the Gentiles? Yes, of the Gentiles also, since there is one God who will justify the circumcised by faith and the uncircumcised through faith. Do we then make void the law through faith? Certainly not! On the contrary, we establish the law. What then shall we say that Abraham our father has found according to the flesh? For if Abraham was justified by works, he has something to boast about, but not before God. For what does the Scripture say? “Abraham believed God, and it was accounted to him for righteousness.” Now to him who works, the wages are not counted as grace but as debt. But to him who does not work but believes on Him who justifies the ungodly, his faith is accounted for righteousness, just as David also describes the blessedness of the man to whom God imputes righteousness apart from works: “Blessed are those whose lawless deeds are forgiven,And whose sins are covered; Blessed is the man to whom the Lord shall not impute sin.” Does this blessedness then come upon the circumcised only, or upon the uncircumcised also? For we say that faith was accounted to Abraham for righteousness. How then was it accounted? While he was circumcised, or uncircumcised? Not while circumcised, but while uncircumcised. And he received the sign of circumcision, a seal of the righteousness of the faith which he had while still uncircumcised, that he might be the father of all those who believe, though they are uncircumcised, that righteousness might be imputed to them also, and the father of circumcision to those who not only are of the circumcision, but who also walk in the steps of the faith which our father Abraham had while still uncircumcised. For the promise that he would be the heir of the world was not to Abraham or to his seed through the law, but through the righteousness of faith. For if those who are of the law are heirs, faith is made void and the promise made of no effect, because the law brings about wrath; for where there is no law there is no transgression. Therefore it is of faith that it might be according to grace, so that the promise might be sure to all the seed, not only to those who are of the law, but also to those who are of the faith of Abraham, who is the father of us all (as it is written, “I have made you a father of many nations”) in the presence of Him whom he believed—God, who gives life to the dead and calls those things which do not exist as though they did; who, contrary to hope, in hope believed, so that he became the father of many nations, according to what was spoken, “So shall your descendants be.” And not being weak in faith, he did not consider his own body, already dead (since he was about a hundred years old), and the deadness of Sarah’s womb. He did not waver at the promise of God through unbelief, but was strengthened in faith, giving glory to God, and being fully convinced that what He had promised He was also able to perform. And therefore “it was accounted to him for righteousness.” Now it was not written for his sake alone that it was imputed to him, but also for us. It shall be imputed to us who believe in Him who raised up Jesus our Lord from the dead, who was delivered up because of our offenses, and was raised because of our justification.

Bible Gateway passage: Romans 3:21-4:25 - New King James Version
God’s Righteousness Through Faith - But now the righteousness of God apart from the law is revealed, being witnessed by the Law and the Prophets, even the righteousness of God, through faith in Jesus Christ, to all and on all who believe. For there is no difference; for all have sinned and fall...
Paul says we are not justified by works, but by FAITH!
Paul also references Genesis 15, but instead of it being in the context of works, he says that Abraham was justified BEFORE he did any works! Remember the "work of the flesh" I mentioned above? "How then was it accounted? While he was circumcised, or uncircumcised? not while circumcised, but while uncircumcised." Abraham was circumcised while uncircumcised! He was already justified by his faith: "He believed God, and it was accounted to him for righteousness!"
James: Abraham was justified by works.
Paul: Abraham was justified by faith and not of works.
Paul clarifies: "For if Abraham was justified by works, he has something to boast about, but not before God. For what does the Scripture say? "Abraham believed God, and it was accounted to him for righteousness." Now to him who works, the wages are not counted as grace but as debt. But to him who does not work, but believes on Him who justifies the ungodly, his faith is accounted for righteousness, just as David also describes the blessedness of the man to whom God imputes righteousness apart from works."
Of course I'm interpreting James in light of Paul!
The way in which you are doing it is incorrect, and thus causing confusion.
But that's only making him say something other than the plain reading if you discount Paul. Plain reading is not achieved by reading a single scripture in a vacuum, as you have consistently (and rightly) pointed out to me on other subjects.
Indeed.
Which means that if you ignore the context of Acts, you're going to mash scriptures together that were not intended to be mashed together.
I don't see how that scripture is related to what you wrote above. Peter was obviously living like the Gentiles (appropriately, according to Paul),
Appropriately?
So why did Paul "withstand him to his face"? Why did Paul place blame on him for living like a Gentile when the men from James were not around, but separated himself when they were? Such hypocrisy caused even Barnabas to be carried away!
and only changed his manner of living, and required others to do the same, when some men from James came around. How does showing that Peter was agreeing with Paul help your argument?
He was being a hypocrite!
Peter would live like a Gentile, but when the men from James came, he lived as though he was justified by works, and not by faith only! (cf Galatians 1:16)
Who said they did?
James did.
James: Faith without works is dead, and cannot save.
You: We are saved by and show our faith is living by doing works.
Do you not see the difference between those?
Yes. And James agrees with that.
[Jas 2:23 KJV] And the scripture was fulfilled which saith, Abraham believed God, and it was imputed unto him for righteousness: and he was called the Friend of God.
Supra. Paul teaches that one is justified by FAITH, and not of works.
James teaches the exact opposite! He teaches that you must have works, or your faith is dead, and cannot save, that you are justified by works, and not by faith only.
Of course not. But for it to be real faith.
Was the thief on the cross justified by faith or by works?
If the latter, what works did he do that justified him?
Right. Nothing we do can add to Christ's work on the cross.
James is saying the opposite. "Do you see that faith was working together with his works, and by works faith was made perfect?" (2:22)
Paul says if you work, it's not grace, but debt! There's something to boast about, but not before God. The idea runs counter to our faith being "alone" rather than "accompanied by works."
But we can't show our faith in Christ without works. If you say you believe in your mind and heart that God raised Jesus from the dead, but you are continually afraid of God's judgment, such that you eat and drink for tomorrow you may die, then are you saved or not? The answer is "I don't know, and neither do you." Because your actions are inconsistent with your supposed faith.
False.
The answer is if you profess the name of the Lord Jesus and believe in your heart God has raised Him from the dead, you will be saved. That's a guarantee! It's a guarantee that is not and CANNOT be affected by anything we do, else IT WOULDN'T BE GRACE!!!
It's nothing that WE DO that saves us!
James asks "can faith save someone if they do not have works?" and he asks with the answer being "NO!" in his mind, and says as much: "Faith without works is dead!"
It is, because you can't tell that a man is justified by faith unless his works also testify that he has faith. Can God tell? Maybe. But if God sees that you believe in your heart, but never put your faith into practice, does He even believe it? Perhaps not:
[Rom 10:9 KJV] That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
If someone has done what Romans 10:9-10 said, his faith is accounted to him for righteousness. He is justified by faith, BEFORE works. He is saved by grace through faith (because Romans 10:9-10 is the expression of faith), NOT OF WORKS, lest he boast.
If he worked, then he has something to boast about, but not before God!
That runs counter to what James said: "What does it profit . . . if someone says he has faith but does not have works?"! NOTHING! There's no salvation!
According to James, if all you have is faith, your faith is dead, it cannot save.
According to Paul, your faith, not any works, is what justifies you!