John Calvin Commentary Romans 9:23

"and that he might make known the riches of his glory upon vessels of mercy, which he afore prepared unto glory," — Romans 9:23 (ASV)

That he might also make known the riches of his glory, etc. I do not doubt that the two particles καὶ ἵνα are an instance of a construction where the first word is put last (a figure of speech known as ὕστερον πρότερον); and, so that this clause may better unite with the former, I have translated it, That he might also make known, etc. (Ut notas quoque faceret, etc.).

This is the second reason that reveals the glory of God in the destruction of the reprobate: the greatness of divine mercy towards the elect is in this way more clearly made known. For how do they differ from them, except that they are delivered by the Lord from the same gulf of destruction? And this is by no merit of their own, but through His free kindness. Therefore, it must be that the infinite mercy of God towards the elect appears increasingly worthy of praise when we see how miserable all those are who do not escape His wrath.

The word glory, mentioned here twice, I consider to be used for God’s mercy—a metonymy of the effect for the cause, for His chief praise or glory consists in acts of kindness. So in Ephesians 1:13, after he has taught us that we have been adopted to the praise of the glory of his grace, he adds that we are sealed by the Spirit of promise unto the praise of his glory, with the word “grace” being omitted in the second instance. Therefore, he wished to show that the elect are instruments or vessels through whom God exercises His mercy, so that through them He may glorify His name.

Although in the second clause he asserts more explicitly that it is God who prepares the elect for glory—just as he had simply said before that the reprobate are vessels prepared for destruction—yet there is no doubt that the preparation of both is connected with the secret counsel of God. Paul might have otherwise said that the reprobate give themselves over to destruction or cast themselves into it; but he indicates here that, before they are born, they are destined to their lot.