Romans 4:1-12
If a ladder is too short to reach a high object, a man standing on the highest rung is no more able to reach it than those who are beneath him. "There is no difference" we have read (Romans 3:22); the Jew no more than the Gentile has not attained to the glory of God. Nobody gets there by the ladder of his own righteousness; it will always be insufficient. The proof of this is seen in that even Abraham (v. 3) and David (v. 6), who would unquestionably have had the right to consider themselves on the highest step of this ladder of good works, even they have not been able in this way to justify themselves before God. And if they cannot do this, who else could claim to do it? To demonstrate absolutely that salvation by grace has no relationship with fleshly pretensions and the "boasting" of the Jewish race (Romans 3:27), vv. 9, 10 recall that the patriarch Abraham was justified by faith before the sign of circumcision (Genesis 15:6; Genesis 17:24). At the time when God justified him, he was still in the same position as the heathen.
In order to be saved, a man must begin by recognising himself as guilty; in other words, he agrees with the divine sentence mentioned in the preceding chapter. It is "the ungodly" and him alone, whom God justifies (v. 5; cf. Matthew 9:12).