It may be a bit difficult to understand the meanings of righteousness and justification. These terms were already used by Mikael Agricola. He translated the words dikaiosynee (subst.) and dikaios (adj.) found in the Greek Bible. The word dikaiosynee (lat. Iustificatio) was a secular, legal term in the Roman Empire. It meant justice.
In a spiritual sense, justification means restoring. A righteous man is restored to the state where man was before the fall into sin. He is forgiven his sin completely without his own merit and has become holy before God. Faith in Christ's crucifiction has saved him. Christ has fulfilled the will of God, the law, on our behalf, and reconciled our sin for us in our stead. In the presence of God, a justified person is holy and immaculate. The blood of Christ continuously cleanses us.
Luther writes in the Schmalkald Articles: “What I have hitherto and constantly taught concerning this I know not how to change in the least, namely, that by faith, as St. Peter says, we acquire a new and clean heart, and God will and does account us entirely righteous and holy for the sake of Christ, our Mediator. And although sin in the flesh has not yet been altogether removed or become dead, yet He will not punish or remember it.”
The Apostle Paul writes in Romans 3:
19Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God.
20 Therefore no one will be declared righteous in God’s sight by the works of the law; rather, through the law we become conscious of our sin.
21 But now apart from the law the righteousness of God has been made known, to which the Law and the Prophets testify.
22 This righteousness is given through faith in Jesus Christ to all who believe. There is no difference between Jew and Gentile,
23 for all have sinned and fall short of the glory of God,
24 and all are justified freely by his grace through the redemption that came by Christ Jesus.
25 God presented Christ as a sacrifice of atonement, through the shedding of his blood—to be received by faith. He did this to demonstrate his righteousness, because in his forbearance he had left the sins committed beforehand unpunished—
26 he did it to demonstrate his righteousness at the present time, so as to be just and the one who justifies those who have faith in Jesus.
27 Where, then, is boasting? It is excluded. Because of what law? The law that requires works? No, because of the law that requires faith.
28 For we maintain that a person is justified by faith apart from the works of the law.
Or is God the God of Jews only? Is he not the God of Gentiles too? Yes, of Gentiles too,
30 since there is only one God, who will justify the circumcised by faith and the uncircumcised through that same faith.
31 Do we, then, nullify the law by this faith? Not at all! Rather, we uphold the law.
It is said, and it is perfectly true, that our Christianity and our beliefs are standing or crashing with the doctrine of justification. It is the center of everything, the core of our faith. There must be no slight change in it. Whatever else is taught about Christianity and faith, it must be in harmony with the doctrine of justification. It concerns sanctification, teaching concerning the congregation, "spiritual government," counseling, etc.
Freedom of belief must not be bound, not through the law of God, nor in the rules or conditions of mankind. The Spirit of God is free and we are the children of the free Son.
Often we are discussing the boundaries of the congregation. "Lord, are there so little that are saved?" That question is well answered by the Saviour. “Make every effort to enter through the narrow door, because many, I tell you, will try to enter and will not be able to (Luke 13: 23-24). Jesus answers the church question by turning the questioner's thought into how to be righteous before God. Only when all of his own is stripped is man willing to receive the bounty of grace made in Christ. We must remain as spiritually poor our whole life, nor when death comes are we asked of anything other than faith in Christ.
The sinner is holy, the unclean is clean and the wrong is righteous. This is the secret of reconciliation, which is not understood by reason, but which we sinners possess by faith.