"Justification is an act of God where a sinner is made righteous...

"Justification is an act of God where a sinner is made righteous hence justified because of that sinner’s faith in Christ."
Correct, as taught in 1 Cor 15:1-4
"It has nothing to do with works"
Correct again - Eph 2:8-9, Gal 2:16, Rom 3:24-28, Rom 4:5-8, Rom 5:1, Titus 3:5, Eph 1:13, Eph 4:30
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Now where does Paul teach that above a certain LEVEL of sin by a SAVED/JUSTIFIED believer = they were never saved/justified in the first place ?