Justification is an act of God's free grace, in which He pardons all our sins, and accepts us as righteous in His sight, only for the righteousness of Christ imputed to us, and received by faith alone.
(ESV Global Study Bible Notes) “What does it mean to be “justified”? To be justified means to be declared righteous before God. It means that, as the divine judge, God looks on those who are in Jesus and declares them “guilty as charged, but pardoned and accepted.”
Do you have a favorite passage in Scripture? I do, it is Romans 3:21-26 because it gives the answer as to how a just God can declare the unrighteous righteous in his sight and keep His own righteousness.
The New American Standard Bible (1995) translators titled this passage, “Justification by Faith.” In other words, those who are justified in the sight of God are the ones who have faith in Jesus.
2 Corinthians 5:21 (NASB) “He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him.”