This study is based upon the New City Catechism.
For by a single offering he has perfected for all time those who are being sanctified. (Hebrews 10:14)
The Christian life is a meeting place of two distinct realities. It is Martin Luther’s formula, simul justus et peccator, which is Latin for, “Simultaneously righteous and fallible.” The Christian is one who is at the same time righteous and unrighteous, just and sinner. He is righteous by divine declaration, and sinner by the sin which remains in him. He is righteous by legality and unrighteous by nature. He is just in the courtroom and unjust in the street.
This dual reality is reflected in Hebrews 10:14, speaking of Christ: “For by a single offering he has perfected for all time those who are being sanctified.” His crucifixion was a single offering, for He died to never die again. Bulls and goats had to be sacrificed every year, for they could not cleanse the worshipers (vv.2-4). Christ’s death was effectual (1 John 2:1-2) unto the end that certain people be perfected for all time (Hebrews 10:14). Their perfection was accomplished in the atoning death of Christ.
Who are we talking about, though? Who are these people who are perfected for all time by Christ’s single offering? Those who are being sanctified. The word “sanctified” means, “to be made holy.” The perfecting mentioned earlier in the verse is said to have been accomplished in Christ’s death, but this “being made holy” is said to be a process: they are being sanctified (emphasis mine). This is a reference only applicable to the people of God. “You shall be holy, for I the Lord your God am holy” (Leviticus 19:2). “And now I commend you to God and to the word of his grace, which is able to build you up and to give you the inheritance among all those who are sanctified” (Acts 20:32). “Even as he chose us in him before the foundation of the world, that we should be holy and blameless before him” (Ephesians 1:4). “For God has not called us for impurity, but in holiness” (1 Thessalonians 4:7).
So, those who are being made holy have been perfected. Those who are within the process of sanctification have had the work of justification accomplished for them in Christ’s death. Justification comes first, when we are declared righteous before God. Sanctification immediately follows, when we are gradually conformed to God’s righteousness in the way we live our lives. Justification is Christ’s righteousness accounted to us in a legal declaration. Sanctification is the growing of our own righteousness, progressively while we live on earth. Justification is a completed, finished work. Sanctification will not be complete until our glorification. In other words, we are simultaneously righteous and fallible.
Much confusion has persisted among believers regarding the nature of justification and sanctification, much to do with the Roman Catholic doctrine of infused righteousness, in opposition to imputed righteousness. Rome teaches that justification is God’s act of infusing Christ’s righteousness into His people, as one may infuse two metals by welding. Our works inevitably become part of our justification, which is why mortal sins may remove us from a justified state.
Contrary to this, the Protestant Reformation clarified that God does not infuse, but imputes Christ’s righteousness to His people. Paul asked for Onesimus’ wrongs and debts to be imputed to him: “If he has wronged you at all, or owes you anything, charge that to my account” (Philemon 18), so that Philemon would receive Onesimus as he would receive Paul (v.17). Paul elsewhere argued that Abraham was justified by faith while he was still uncircumcised (Romans 4:11), for Christ’s righteousness was imputed to him when he believed God, and it was counted (i.e. imputed) to him as righteousness (v.3).
Question: What do justification and sanctification mean?
Answer: Justification means our declared righteousness before God. Sanctification means our gradual, growing righteousness.
 By “accomplished,” we do not mean saving faith and the subsequent declaration of righteousness, which is the fullness of justification, for those who have yet begun the process of sanctification. We mean “accomplished” in the sense that Hebrews 10:14 gives it, that those who are being sanctified have already come to Christ in saving faith, and therefore have already been justified, and therefore may look upon the death of Christ as the secure deposit of all such benefits.