Whole books have been written on justification and imputation. I am not going to attempt to replicate them or give as full of a treatment. My purpose here is only to give an overview.
Let’s start with the term impute or imputation. It comes from Latin and is an accounting term that means “to apply to one’s account.” In finances, expenses are debited and income is credited. So, if something is imputed to you, it is credited to you or your account. The Reformer’s chose this term to differentiate it from the term the Roman Catholic church used which is infuse or infusion. When something is infused it is added to and mixed in with what is already there. Some people have health conditions that require them to receive infused medication. Instead of receiving a pill or a shot, they spend hours hooked up to an IV that drips and infuses the medication into their blood. An example of this is chemotherapy. Theologically, the term double imputation is used. Consider 2 Cor. 5:21:
“For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God.”
This verse (though not only this verse) shows us double imputation. The first imputation is that of ours sins being imputed to Christ: “for our sake he made him to be sin.” Our sins were not infused into Christ’s as He “knew no sin.” No, our sins were imputed to Christ. Though He had never sinned he took upon Himself all our sins. God did this so that Christ’s death could atone for our sins. Jesus had no sins of His own to atone for but by imputation, he had our sins to atone for. The second imputation is that His righteousness was imputed to us: “so that in him we might become the righteousness of God.” The righteousness of God is a righteousness that only God can have. We can never, on our own, posses such righteousness. We become “the righteousness of God” through the imputation of Christ’s righteousness.
Infusion says Christ’s righteousness is added to ours and it is this mixed righteousness that becomes our righteousness before God. What can we add to the righteousness of God? Since God’s righteousness is perfect and complete there is nothing we can add to it. Can you add more time to eternity? Can you add more numbers past infinity? If you have the righteousness of God then you have perfect and complete righteousness. The very righteousness of God Himself! That is what this verse teaches us. Christ took on our sin and atoned for it so that we could take on His righteousness and be saved. One theologian said that two of the most beautiful words in the Bible are for us. Jesus lived, died, and resurrected for us. For us, He took our sins upon Himself and shed His blood to atone for them and gave us His righteousness.
Underlining has been added for emphasis:
For in it the righteousness of God is revealed from faith to faith; as it is written, “BUT THE RIGHTEOUS man SHALL LIVE BY FAITH.” (Romans 1:17)
For the promise to Abraham or to his descendants that he would be heir of the world was not through the Law, but through the righteousness of faith. (Romans 4:13)
What shall we say then? That Gentiles, who did not pursue righteousness, attained righteousness, even the righteousness which is by faith (Romans 9:30)
But now apart from the Law the righteousness of God has been manifested, being witnessed by the Law and the Prophets, even the righteousness of God through faith in Jesus Christ for all those who believe; for there is no distinction (Romans 3:21-22)
But by His doing you are in Christ Jesus, who became to us wisdom from God, and righteousness and sanctification, and redemption (1 Cor 1:30)
Note here we become “righteousness and sanctification and redemption.” Sanctification is listed as separate from righteousness and after it.
For Christ is the end of the law for righteousness to everyone who believes (Romans 10:4)
“In His days Judah will be saved, And Israel will dwell securely; And this is His name by which He will be called, ‘The LORD our righteousness.’” (Jeremiah 23:6)
“For if by the transgression of the one, death reigned through the one, much more those who receive the abundance of grace and of the gift of righteousness will reign in life through the One, Jesus Christ.” (Romans 5:17)
Note that righteousness is a gift. If it was something, even in part, we earned it would not be a gift.
But to the one who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness (Romans 4:5)
Here we see the world credited which is the same concept as imputation. This verse expressly says faith is “credited as righteousness” to “the one who does not work, but believes in Him who justifies the ungodly.” God justifies “the ungodly.” That does not sound like someone who has had Christ’s righteousness infused into his own. Were that the case, he would not be ungodly. What is credited to him as righteousness? His faith. It is his faith, not his works that are credited as righteousness.
I will rejoice greatly in the LORD, My soul will exult in my God; For He has clothed me with garments of salvation, He has wrapped me with a robe of righteousness, As a bridegroom decks himself with a garland, And as a bride adorns herself with her jewels. (Isaiah 61:10)
For as through the one man’s disobedience the many were made sinners, even so through the obedience of the One the many will be made righteous (Romans 5:19)
for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus (Romans 3:26)
Who does God justify? The “one who has faith in Jesus.” Faith, not works.
and may be found in Him, not having a righteousness of my own derived from the Law, but that which is through faith in Christ, the righteousness which comes from God on the basis of faith (Phil 3:9)
Again, our righteousness is not derived from the Law (works) but “through faith in Christ.” That righteousness “comes from God on the basis of faith.”
I hope these verses show that we are justified on the basis of having been imputed the righteousness of Christ on the basis of our faith in Him, itself a gift of God.
As I have previously written, sanctification necessarily follows justification. Sanctification is an ongoing and progressive work in our lives as we gradually become more and more like Jesus Christ:
For I am confident of this very thing, that He who began a good work in you will perfect it until the day of Christ Jesus (Phil 1:6)
Sanctification is that ongoing work that God has begun and will one day perfect.
One misconception I find about salvation by faith alone, is that it becomes a license to sin. Since you are “saved by faith alone” then you can sin all you want once you express faith. Paul addressed this and wrote “May it never be!” Here is the fallacy in that. First, you can express faith but not possess faith. In other words, no expression of faith saves you unless you truly possess faith. You can say all the right words but if in your heart you don’t truly believe what you are saying then that is a counterfeit faith. Ever heard the term, “foxhole faith?” It’s been said “there are no atheists in foxholes.” In times of crisis men will sometimes cry out to God for protection or deliverance. Such faith may not be genuine. It may be just a “hail mary” (i.e. just in case God exists I will ask for his help). That’s not to say deathbed faith or foxhole faith is never genuine. God, who alone sees the heart, knows. True faith, while it can be born in a crisis, remains even when the crisis has passed. In His parable of the seed, Jesus talks about how some of the seed sown gets choked out by weeks or never grows. There are those who respond to an invitation of faith, but we see over time that their faith was not genuine. The thief on the cross, one might say, was a “foxhole believer” yet Jesus said he would be with Him that day in Paradise. While his faith might have been expressed under extreme crisis, He possessed true saving faith.
I wrote previously, that God saves us to “walk in good works He prepared beforehand for us.” If you truly possess saving faith it will produce fruit in your life. When God declares you just on the basis of Christ’s righteousness through your faith, He doesn’t just change your status from sinner to saint and then leave you alone. That is a misconception! That is not what salvation by faith alone teaches! When God saves you, He changes you. You are given a new nature. That new nature cannot help but produce faith. Thus, a changed man will not have an attitude of “I can sin all I want because I am saved by faith alone.”
When we realize how sinful our sin is, and how Christ took our sin upon Him, how can we not want to please and obey Him? If someone saves your life, would you not be grateful to them? If we would be grateful to someone who saved our physical life, would we not be much more grateful to someone who saves our spiritual life and thus our eternal soul?
Sometimes, to try and question salvation by faith alone, people will put hypothetical questions to you like “Could you murder someone, feel no remorse, and still be saved?” My answer would be no! It’s possible a saved person could murder someone (though unlikely) but not without remorse. The Holy Spirit would convict their conscience of their sin. Usually these hypothetical questions presuppose situations that would never occur with a truly saved person. However, if you answer (even with qualification) that yes that person would still be saved, they say “Aha! See, you don’t think how someone lives matters at all. You can say you believe, live like the devil, but still be saved.” If someone is “living like the devil”, and never repents, then I would seriously question their possession of saving faith. I would suspect they never had saving faith and thus are not saved. It is exactly this time of “easy believism” that James and other NT authors write against. Their writings do not teach that we need works to be saved, but that without works we weren’t saved. God does not wait to see those works before He saves us. He saves us when we possess no good works, but transforms us such that good works necessarily follow.
I believe the key to all this, is to understand that saving faith is a gift. God choses who receives this gift. The possession and expression of saving faith is a work of God through us. Without that gift, we can express faith but it is an empty faith and not from God. We should not confuse the two. If you merely express faith without possessing it, you might “live like hell” or have an attitude that you can sin all you want because you are saved by grace, but you will be mistaken and find yourself on Judgment Day hearing “I never knew you; depart from Me, you who practice lawlessness.” (Matthew 7:23)