5 But [de] to him that worketh [ergazomai] not [me], but [de] believeth [pisteuo] on [epi] him that justifieth [dikaioo] the ungodly [asebes], his [autos] faith [pistis] is counted [logizomai] for [eis] righteousness [dikaiosune]. KJV-Interlinear
5 And to
the one who does not work but believes in him who justifies the ungodly, his
faith is counted as righteousness, ESV
The key phrase here is, the ungodly. For all of humanity is flawed and sinful and are failures in the sight of God, who is perfect.
No person can match or even come close to the perfection of God.
God has never failed, and never will. God has never transgressed, and never will.
But man, has failed over and over, again, and again, and thus the total depravity of man makes him unqualified to come to God of his own accord.
So, for the person who does not seek atonement by means of his own work, but instead seeks it by means of the work of God, then that belief or faith, is the mechanism for acquiring his perfection.
For not by anything we can do, are we saved, but by means of what God has done and our belief in that work, are we saved.
All of man is ungodly.
He who justifies the ungodly, is God.
Jesus Christ is the one who did the work, and is in fact God, both God and man in one person, the unique person of the universe and of all of existence.