John Calvin Commentary Romans 2:1

"Wherefore thou art without excuse, O man, whosoever thou art that judgest: for wherein thou judges another, thou condemnest thyself; for thou that judgest dost practise the same things." — Romans 2:1 (ASV)

Therefore you are inexcusable, O man. This reproof is directed against hypocrites, who dazzle the eyes of people by displays of outward sanctity, and even think themselves to be accepted before God, as if they had given Him full satisfaction. Therefore Paul, after having stated the grosser vices, so that he might prove that no one is just before God, now attacks saintlings (sanctulos) of this kind, who could not have been included in the first list.

The inference is so simple and plain that no one should wonder how the Apostle derived his argument. For he makes them inexcusable, because they themselves knew the judgment of God and yet transgressed the law. It is as if he said, “Though you did not consent to the vices of others, and seem to be avowedly an enemy and a reprover of vices, yet as you are not free from them, if you really examine yourself, you cannot bring forward any defense.”

For in what you judge another, etc. Besides the striking resemblance between the two Greek verbs, κρίνειν and κατακρίνειν (to judge and to condemn), the enhancing of their sin should be noted. For his way of speaking is the same, as if he said, “You are doubly deserving of condemnation, for you are guilty of the same vices which you blame and reprove in others.” It is, indeed, a well-known saying — that those who scrutinize the life of others themselves lay claim to innocence, temperance, and all virtues; and that those are not worthy of any indulgence who allow in themselves the same things which they undertake to correct in others.

For you, judging, do the same things: so it is literally; but the meaning is, “Though you judge, you still do the same things.” And he says that they did them because they were not in a right state of mind; for sin properly belongs to the mind. They then condemned themselves on this account — because, in reproving a thief, or an adulterer, or a slanderer, they did not merely condemn the persons, but those very vices which adhered to themselves.