Are you aware that Paul takes 11 chapters in his letter to the Romans to teach both Jew and Gentile how they are justified by faith?
To claim justification by faith is only old testament is to ultimately ignore its teaching in the new testament.
Moreso, salvation by faith is not taught in the Bible, OT or NT. It's always been salvation by grace.
It is dishonest to set up a straw man and argue against him. I did not say justification by faith is only an OT doctrine, nor would I say it, because it is not true. I spelled out what I meant and it was clear.
God justifies the sinner because the judge is the only one who can do it. He does not have to do it if there is guilt involved and the judge says all have sinned. However, the judge has said in the OT that he would justify sinners for believing what he said to them and impute their faith in him for righteousness. So then, justification is by faith just like the Judge says. In the NT the judge has devised a way that a guilty man could have someone else pay his penalty that the Judge has prescribed for sinners, which is death, and the sinner would then have no guilt and would have perfect righteousness before the Judge and could go free. The Judge did not have to accept the sacrifice but it was the Judge who provided the sacrifice, his own Son. In doing this, the Judge could also grant forgiveness of sin for the justified believers of the OT.
Here are two passages that deals with the OT believers in what God said to them. Read them and consider them.
Rom 3:24 Being justified freely by his grace through the redemption that is in Christ Jesus:
25 Whom God hath set forth [to be] a propitiation through faith in his blood, to declare his righteousness for the remission of
sins that are past, through the forbearance of God;
26 To declare, [I say],
at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
27 Where [is] boasting then? It is excluded. By what law? of works? Nay: but by the law of faith.
28 Therefore we conclude that a man is justified by faith without the deeds of the law.
13 For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:
14 How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?
15 And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions [that were] under the first testament, they which are called might receive the promise of eternal inheritance.
16 For where a testament [is], there must also of necessity be the death of the testator.
17 For a testament [is] of force after men are dead: otherwise it is of no strength at all while the testator liveth.
Therefore it is the obedience of Christ to God and his shed blood in both testaments that saves sinners and the principle for the application of that blood is the same in both testaments. It is FAITH in what God says. As sure as the blood was applied on the doorposts of the Israelites in Egypt on the first Passover as a type of faith in what God said to do to be saved from the death angel, one must obey God and apply the blood of Christ by faith. Hyssop, that which was provided by the man, is a picture of faith. He applied the blood with it.
The theology of justification is given in Rom 3. Then God gives us three practical illustrations of this justification by faith doctrine in Rom 4. The categories are in times.
1) Abraham - Before the Law of Moses
2) David during the law of Moses
3) Believers after the law of Moses and after the cross.
The point of this is to show that God's method of dealing with men may change, the means of justification of sinners is constant. It is by faith in what he says to sinners.
We know what he said to Abraham and how he responded. We know what he said to David and how he responded. But what does he say to us today? Here it is.
21 And being fully persuaded that, what he (God) had promised, he was able also to perform.
22 And therefore it was imputed to him (Abraham) for righteousness.
23 Now it was not written for his sake alone, that it was imputed to him;
24 But for us also, to whom it shall be imputed, if we believe on him (God) that raised up Jesus our Lord from the dead;
25 Who was delivered for our offences, and was raised again for our justification.
One cannot be justified by believing what Abraham or David believed by which they were justified. We must believe in Jesus Christ who died for us and was buried and rose again. We must believe what God says about it. What does he say? Here it is;
Rom 8:32 He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things?
33 Who shall lay any thing to the charge of God’s elect?
[It is] God that justifieth.
34 Who [is] he that condemneth? [It is] Christ that died, yea rather, that is risen again, who is even at the right hand of God, who also maketh intercession for us.
You see how God justifies and reckons the believer in the death and resurrection of Jesus Christ to be righteous and without guilt that can condemn him?
Back to Rom 4. Read this;
22 And therefore it was imputed to him for righteousness.
23 Now it was not written for his sake alone, that it (righteousness) was imputed to him;
24 But for us also, to whom it (righteousness) shall be imputed, if we believe on him (GOD) that raised up Jesus our Lord from the dead;
We must believe the record that God has given of his Son in order to be saved from the penalty of sin. This is the fundamentals of the faith , and your list of fundamentals as a Calvinist are not included.
Ponder these things.