And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses.
Note 13 at Ac 13:39: Justification is the act of God that makes us totally righteous in His sight. To accomplish this, the Lord not only forgives our sins but also imparts His righteousness. This makes us "just-as-if-I'd" never sinned or "justified."
Under the Old Testament Law, many things were unpardonable and carried the death sentence (examples - the eating of blood, Le 17:10-14; sexual sins, Le 18:6-30; offering of children to Molech, Le 20:2-5; involvement in the occult, Le 20:6 and 27; cursing parents, Le 20:9; etc.). Through Jesus, we can now receive forgiveness from these things and enjoy right-standing with God.