Job asks the all important question in Job 25:4, "How can a man be justified with God?" Paul answers the question in Romans 5:1 stating that we are justified by faith.
Justification is the judicial act of God whereby He legally declares the believing sinner to be innocent of all sin and as perfectly righteous as Christ. This act of justifying believing sinners comes only through faith and by the grace of God. (Rom. 5:1; Rom. 3:24)