"If God justifies sinners freely by His grace, on what grounds does He do so? How is it possible for the righteous God to declare the unrighteous to be righteous without either compromising His righteousness or condoning their unrighteousness? This is our question. God's answer is the Cross".
John R W Stott - "BST Series - The Message of Romans" - IVP, Leicester (1994) - (p112).