If God saves us, what is his specific reason, his specific warrant, as it were, for doing so? One could imagine God saving us on a whim, but being just, God always has valid reasons for doing what he does.
According to the biblical testimony, God saves us because we are righteous. But given that we are sinners, how can we be righteous?
[For proof that all of us are sinners, see, e.g., Romans 3:23 and 1 John 1:8.
For proof that some of us are also righteous, see, e.g., 2 Corinthians 5:21 and Philippians 3:9.]
Well, if God declares us to be righteous, then you can be assured that we are. As we said, God always has valid reasons for doing whatever he does. And if we are righteous, then all of the other benefits (and “side effects”) of salvation will most assuredly occur: sanctification, love, good works, perseverance, repentance from sin, and so on.
So on what basis does God declare us righteous? Scripture declares that God does so on the basis of faith alone. See, e.g., Romans 3:28
Therefore we conclude that a man is justified by faith without the deeds of the law.
Justified” means “declared [or proved] righteous.”
[All Bible quotes here are from the King James Version, unless indicated otherwise. When necessary, we use a translation that indicates more accurately what the original writing said.]
And also see Philippians 3:9:
…and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith… [ESV]
See also Genesis 15:6:
And he [Abraham] believed in the Lord; and he [God] counted it to him for righteousness.
And also see Romans 4:20—25, in which the Apostle Paul comments on Genesis 15:6:
He [Abraham] staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; And being fully persuaded that, what he had promised, he was able also to perform. And therefore it was imputed to him for righteousness. Now it was not written for his sake alone, that it was imputed to him; But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; Who was delivered for our offences, and was raised again for our justification.
These verses, and others, speak of imputed righteousness. Us getting credit for a righteousness that we do not naturally have, a righteousness that comes from God; specifically God the Son, Jesus Christ. This is why Protestants emphasize faith: Faith in Christ gets the entire enterprise moving. Faith is the ground of salvation.
Now, true faith in Christ issues in all sorts of other goods: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control, and all of the other benefits of salvation. And the lack of these is primary evidence of lack of faith.
But here is the key point for this essay: When Scripture speaks with precision about the actual cause of our salvation, it identifies it to be imputed righteousness as a result of our faith.
To be sure, our repentance and faith are themselves gifts of God. But they are the mechanism, as it were, of our salvation.
There is also the question of exactly how we get this saving faith. Romans 10:17 says that faith comes from hearing the word of Christ, that is, the Bible, and Ephesians 2:8—9 say that faith is a gift of God.
And there is also the question of how faith removes our sins. First Peter 2:24 says that our sins were transferred to Christ on the cross, where he atoned for them, so that we no longer are guilty of sin.
When the Bible speaks of individuals as being righteousness, it does not always identify what exactly makes them righteous. And we are prone to think that it must be that they are exceptionally good at avoiding sin, because this opinion is the default belief of mankind. But this would be a mistake. We must interpret Scripture in light of Scripture. In both the Old and New Testaments, whenever Scripture speaks of the cause of someone being righteous, that cause is faith in God or, since the coming of Messiah, faith in Christ.