God is infinitely holy and as such He cannot overlook our sin. If He did so He would cease to be holy, righteous, just and good. In order to deal with our sin and reconcile us to himself, He has put forth Jesus Christ, the Righteous One. Jesus has become an atonement for our sin through the sacrifice of his life on the cross. He absorbed and satiated the wrath of God that was rightly ours. And now, He stands as our advocate before the Father.
Everyone who repents and is united to him by faith, has his righteousness credited to their account. The redeemed can have ongoing assurance of their salvation through a life of obedience to his commands, walking as He walked.