I think this debate (faith vs works) rages on because of the obfuscation of just how salvation works. I did a decade long study on this issue when the church I worked for started espousing a belief called "dual covenant theology" (think John Haggee) in which it was supposed that Jews & Christians had separate covenants with God whereby they would be saved, and that Christians shouldn't proselytize Jews.
Well Paul talks about 2 covenants - Works of the Law, and Faith. These two covenants are how a man can be justified as righteous.
Galatians 2:16
nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, so that we may be justified by faith in Christ and not by the works of the Law; since by the works of the Law no flesh will be justified.
The writer of Hebrews sees the same two covenants:
Hebrews 8:6
But now He has obtained a more excellent ministry, by as much as He is also the mediator of a better covenant, which has been enacted on better promises.
7 For if that first covenant had been faultless, there would have been no occasion sought for a second.
8 For finding fault with them, He says, “BEHOLD, DAYS ARE COMING, SAYS THE LORD, WHEN I WILL EFFECT A NEW COVENANT WITH THE HOUSE OF ISRAEL AND WITH THE HOUSE OF JUDAH;
9 NOT LIKE THE COVENANT WHICH I MADE WITH THEIR FATHERS ON THE DAY WHEN I TOOK THEM BY THE HAND TO LEAD THEM OUT OF THE LAND OF EGYPT; FOR THEY DID NOT CONTINUE IN MY COVENANT, AND I DID NOT CARE FOR THEM, SAYS THE LORD.
10 “FOR THIS IS THE COVENANT THAT I WILL MAKE WITH THE HOUSE OF ISRAEL AFTER THOSE DAYS, SAYS THE LORD: I WILL PUT MY LAWS INTO THEIR MINDS, AND I WILL WRITE THEM ON THEIR HEARTS. AND I WILL BE THEIR GOD, AND THEY SHALL BE MY PEOPLE.
12 “FOR I WILL BE MERCIFUL TO THEIR INIQUITIES, AND I WILL REMEMBER THEIR SINS NO MORE.”
13 When He said, “A new covenant,” He has made the first obsolete. But whatever is becoming obsolete and growing old is ready to disappear.
Hebrews 7:18
For, on the one hand, there is a setting aside of a former commandment because of its weakness and uselessness
19 (for the Law made nothing perfect), and on the other hand there is a bringing in of a better hope, through which we draw near to God.
Since death came by sin, it stands to reason that life can only come by righteousness. That is where the two covenants come in. These two covenants are covenants for being justified as righteous.
Galatians 3:21
Is the Law then contrary to the promises of God? May it never be! For if a law had been given which was able to impart life, then righteousness would indeed have been based on law.
But how does that righteousness become ours? It seems the scripture is saying that of the two ways to be declared righteous, only one of these ways can actually impart life.
Galatians 2:21
“I do not nullify the grace of God, for if righteousness comes through the Law, then Christ died needlessly.”
Romans 3:20
because by the works of the Law no flesh will be justified in His sight; for through the Law comes the knowledge of sin.
Romans 4:5
But to the one who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness,
Matthew 5:20
“For I say to you that unless your righteousness surpasses that of the scribes and Pharisees, you will not enter the kingdom of heaven.”
So the mechanism for salvation is righteousness. But what is righteousness? I would define it as the state of being sinless, or the opposite of being a sinner. To be righteous is to be morally perfect or to be without sin as God is without sin. Jesus said in Matthew 5:20 that our righteousness had to surpass that of the most righteous religious people of that day, the scribes and Pharisees. In other words, those super-righteous religious leaders weren’t even good enough. Romans 3 says,
Romans 3:21
But now apart from the Law the righteousness of God has been manifested, being witnessed by the Law and the Prophets,
22 even the righteousness of God through faith in Jesus Christ for all those who believe; for there is no distinction;
23 for all have sinned and fall short of the glory of God,
24 being justified as a gift by His grace through the redemption which is in Christ Jesus;
Romans 3:10
as it is written,
“THERE IS NONE RIGHTEOUS, NOT EVEN ONE;
Here we see from Romans 3:10, 23 that all have sinned and fall short of the standard of righteousness necessary to enter the kingdom of heaven. Paul even quotes scripture (Psalm 14:3, Psalm 53:3) and says that there is no one who is righteous, not even one. All are classified as sinners, and therefore no one deserves life. All justly deserve death, which is the punishment for sin (Romans 6:23 – the wages of sin is death).
So how do we obtain righteousness? Well the Scriptures seem to indicate that there are two ways to be righteous.
Romans 10:5
For Moses writes that the man who practices the righteousness which is based on law shall live by that righteousness.
6 But the righteousness based on faith speaks as follows: “DO NOT SAY IN YOUR HEART, ‘WHO WILL ASCEND INTO HEAVEN?’ (that is, to bring Christ down),
7 or ‘WHO WILL DESCEND INTO THE ABYSS?’ (that is, to bring Christ up from the dead).”
8 But what does it say? “THE WORD IS NEAR YOU, IN YOUR MOUTH AND IN YOUR HEART”—that is, the word of faith which we are preaching,
So to understand the covenant of faith, we have to look at when this covenant was instituted, when it was first created, to see what the terms and conditions of the covenant of faith are, and how they apply to the believer.
Paul looked at this question and wrote books which speak about what is, in my opinion, one of the most amazing revelations of scripture in the book of Romans and Galatians.
Galatians 3:6
Even so Abraham BELIEVED GOD, AND IT WAS RECKONED TO HIM AS RIGHTEOUSNESS.
This is the scriptural basis for faith being the exchange currency for righteousness. Paul shows that the Torah, the law itself, provides the basis for salvation by faith because he is quoting from Genesis 15 (part of the Torah).
Genesis 15:5
And he brought him forth abroad, and said, Look now toward heaven, and tell the stars, if thou be able to number them: and he said unto him, So shall thy seed be.
6 And he believed in the LORD; and he counted it to him for righteousness.
What God showed me was that it wasn’t that Abraham simply believed God when He told him any random thing. The reason Abraham was credited as righteous was because he believed something very specific. For example, if God said “the sky is blue” and I believed Him, it doesn’t make me righteous. Paul continues to lay out the case in Galatians 3 for us:
Galatians 3:16
Now the promises were spoken to Abraham and to his seed. He does not say, “And to seeds,” as referring to many, but rather to one, “And to your seed,” that is, Christ.
According to Paul, when God says to Abraham in Genesis 15:5 “so shall thy seed be” He was talking about Jesus Christ! It wasn’t that Abraham believed any random thing, but rather that God told Abraham specifically about Jesus Christ, and when Abraham believed God regarding Jesus Christ, he was made righteous. Isn’t this the same as we Christians do today? Aren’t we made righteous by believing the gospel of Jesus Christ? Some might say, “but faith comes by hearing and hearing by the word of God.” Yes, that is true and I believe that God Himself was preaching the gospel of Jesus Christ to Abraham and when Abraham believed the gospel of Jesus Christ, he was saved – or made righteous. Paul confirms this in Galatians 3:8:
Galatians 3:8
The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, “ALL THE NATIONS WILL BE BLESSED IN YOU.”
So Abraham was made righteous because God preached the gospel to him and he believed the gospel! This means Abraham was the first “Christian” – the first person saved by grace through their faith in the gospel of Jesus Christ. Paul confirms that Abraham was indeed the first believer:
Galatians 3:7
Therefore, be sure that it is those who are of faith who are sons of Abraham.
Galatians 3:9
So then those who are of faith are blessed with Abraham, the believer.
Luke 19:9
And Jesus said to him, “Today salvation has come to this house, because he, too, is a son of Abraham.”