Justified By The Death and Obedience of Christ
[Christ] was delivered for our offences, and was raised again for our justification.
Much more then, being now justified by his blood, we shall be saved from wrath through him.
Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.
In these passages the Bible speaks of justification as a work accomplished by Christ 2000 years ago as He obeyed the law and died on the cross for His people.
Christ went to the cross, not as a private person, but as the Representative and Substitute of His sheep. He died, not for sins He had committed, but for the sins of all whom He represented.
Their sins were legally charged (imputed) to His account so that God the Father was just to punish His holy, harmless, undefiled Son, for sins.
Christ did all this in order to establish a righteousness for His people so that God could be just to justify them, the ungodly. This was completely accomplished 2000 years ago (John 17:4; John 19:30) so much that God’s elect in the Old Testament were justified based on this righteousness even before it was accomplished in time, and God’s elect in the New Testament era are saved based on its having been accomplished in time.