Are you not surprised that there should be such an expression as that in the Bible, “That justifies the ungodly?” (Rom. 4:15) I have heard that men that hate the doctrines of the cross bring it as a charge against God, that He saves wicked men and receives to Himself the vilest of the vile. See how this Scripture accepts the charge, and plainly states it! By the mouth of His servant Paul, by the inspiration of the Holy Ghost, He takes to Himself the title of “Him who justifies the ungodly” He makes those just who are unjust, forgives those who deserve to be punished, and favors those who deserve no favor. You thought, did you not, that salvation was for the good and that God’s grace was for the pure and holy, who are free from sin? It has fallen into your mind that, if you were excellent, then God would reward you; and you have thought that because you are not worthy, therefore there could be no way of you enjoying His favor.
You must be somewhat surprised to read a text like this: “Him who justifies the ungodly “I do not wonder that you are surprised; for with all my familiarity with the great grace of God, I never cease to wonder at it. It does sound surprising, does it not, that it should be possible for a holy God to justify an unholy man? We, according to the natural legality of our hearts, are always talking about our own goodness and our own worthiness, and we stubbornly hold to it that there must be something in us in order to win the notice of God. Now, God, who sees through all deceptions, knows that there is no goodness whatever in us. He says that “None is righteous, no not one” (Ro 3:10). He knows that “all our righteousness deeds are like a polluted garment”(Is 64:6), and, therefore the Lord Jesus did not come into the world to look after goodness and righteousness with him, and to give them upon persons who have none of them. He comes, not because we are just, but to make us so: he justifies the ungodly.
Charles Spurgeon, All of Grace