Question: "Why does Christ's righteousness need to be imputed to us?"
Answer: We need the righteousness of Christ imputed to us because we have no righteousness of our own. We are sinners by nature, and we cannot make ourselves righteous—we cannot place ourselves in right standing with God. We need Christ’s righteousness imputed to us—meaning, we need His holiness before God credited to our account.
In His Sermon on the Mount, Jesus makes our need for imputed righteousness plain. He says, “You therefore must be perfect, as your heavenly Father is perfect” (Matthew 5:48). This comes after Jesus had just corrected His listeners’ misunderstanding of the law. In Matthew 5:20, Jesus says that, if His hearers want to enter into the kingdom of heaven, their righteousness must exceed that of the Pharisees, who were the experts in the knowledge of the law.
Then, in Matthew 5:21–47, Jesus radically redefines obedience to the law from mere outward conformity, which characterized the “righteousness” of the Pharisees, to an obedience of both outward and inward conformity. Six times in this passage, He says, “You have heard that it was said . . . but I tell you.” In this way, Jesus differentiated the requirements of the law as the people had been taught from its actual requirements. Obeying the law is more than simply abstaining from murder or adultery, for example. It’s also not getting angry with your brother and not lusting in your heart. At the end of this section of the sermon, Jesus says we must “be perfect” (verse 48).
At this point, the natural response is, “But I can’t be perfect,” which is absolutely true. In another place in Matthew’s Gospel, Jesus summarizes the Law of God with two commandments: love the Lord your God with all your heart, soul, mind, and strength, and love your neighbor as yourself (Matthew 22:37–40). These commands also condemn us, because has anyone ever loved the Lord with all his heart, soul, mind, and strength and loved his neighbor as himself? Everything we do, say, and think must be done, said, and thought from love for God and love for neighbor. We have never achieved that level of spirituality. We are not righteous.
Sin affects us to the very core of our being, and no matter how good we try to be, we will never meet God’s standard of perfection on our own. The Bible says that all our righteous deeds are like a “polluted garment” (Isaiah 64:6). Our own attempts at goodness are simply not good enough. We need an imputed righteousness, and for that we look to Christ.
On the cross, Jesus took our sin upon Himself and purchased our salvation. We have “been justified by his blood” (Romans 5:9), and part of that justification is an imputation of His own righteousness. Paul puts it this way: “For our sake [God] made [Jesus] to be sin who knew no sin, so that in him we might become the righteousness of God” (2 Corinthians 5:21). Jesus is righteous by virtue of His very nature—He is the Son of God. By God’s grace, “through faith in Jesus Christ,” that righteousness is given “to all who believe” (Romans 3:22). That’s imputation: the giving of Christ’s righteousness to sinners.
Having Christ’s righteousness imputed to us does not mean we automatically do what is right—that will come through the process of sanctification. What it does mean is that we are positionally righteous; even though we still sin, we are forensically or legally righteous. God has credited the righteousness of Christ to our account, and He did this when He saved us. In grace, the holiness of Jesus Christ is ascribed to us. Christ “has become for us wisdom from God—that is, our righteousness, holiness and redemption” (1 Corinthians 1:30).
By having the righteousness of Christ imputed to us, we can be seen as sinless, as Jesus is sinless. This is amazing grace! We are not righteous in ourselves; rather, we possess Christ’s righteousness applied to our account. It is not our perfection but Christ’s that God sees when He brings us into fellowship with Himself. We are still sinners in practice, but the grace of God has declared us to have righteous standing before the law.
A wonderful illustration of Christ’s imputed righteousness is found in Jesus’ parable of the wedding banquet. Guests are invited to the king’s celebration from every street corner, and they are brought in, “the bad as well as the good” (Matthew 22:10). All the guests have something in common: they are each given a wedding garment. They are not to wear their street clothes in the banquet hall but are to be dressed in the garment of the king’s providing. They are covered in a gracious gift. In a similar way, we, as guests invited into God’s house, have been given the pure white robe of Christ’s righteousness. We receive this gift of God’s grace by faith.