Justification from Eternity !
God's Purpose and Will not to punish sin in the Elect is their Justification from all sin, for God's Purpose not to punish sin in His Elect is Revealed in His Purpose of Christ's Death before the World began,
Rev 13:8
8 And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb
slain[For the sins of the Elect] from the foundation of the world.
1 Pet 1:20
20 Who verily was foreordained[To Be slain for sin]
before the foundation of the world, but was manifest in these last times for you,
These scriptures reveal a valuable FACT that God not never at one Time before the foundation of the World purposed to punish the sins of the Elect in them, hence He never imputed them [their sins] to their charge, this non imputation of their sins from before the foundation of the world, was their acquittal and Justification from all sin from the foundation of the World, for we read of the blessedness of non imputation here
Rom 4:7-8
7 Saying,
Blessed are they whose iniquities are forgiven, and whose sins are covered.
8
Blessed is the man to whom the Lord will not impute sin.