But for us also, to whom it [righteousness] shall be imputed, if we believe on him that raised up Jesus our Lord from the dead;
Who was delivered for our offences, and was raised again for our justification.
Justification is "just as if you never sinned." It is a verdict of acquittal ("Not guilty!") issued by God, the righteous judge, as a result of Jesus Christ's obedience to God's Word. We are justified before God on legal grounds because Christ paid the penalty for our sins.