Romans 3:25-26

Romans 3:25-26 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— 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.

Jesus was a sacrifice of atonement for those who have faith.  In the bad news of Romans one and two it was shown that God’s righteousness required that his wrath against the sin and unrighteousness of mankind must be punished.  All of humanity throughout history are under this wrath as Romans 3:9-18 points out.  Through the blood of Jesus Christ God is able to be just by punishing our sin in our substitute, Jesus Christ, and also justify those who through faith in Christ are counted as righteous.  Our sin is imputed to him and his righteousness is imputed to us in this transaction.  Faith is not meritorious, but is the instrument by which sinners take hold of this salvation.  We are not made righteous but are counted as righteous by this atonement.  We are washed clean by the blood of the Lamb of God that takes away the sin of the world [John 1:29].