Calvin on The Newness of the New Covenant - An Answer to My Question

In my last post I questioned Calvin's view of regeneration in the Old Covenant. As I read further in his comments on Jeremiah 31:31-34, I found this.

" A question may however be here moved, Was the grace of regeneration wanting to the Fathers under the Law? But this is quite preposterous. What, then, is meant when God denies here that the Law was written on the heart before the coming of Christ? To this I answer, that the Fathers, who were formerly regenerated, obtained this favor through Christ, so that we may say, that it was as it were transferred to them from another source. The power then to penetrate into the heart was not inherent in the Law, but it was a benefit transferred to the Law from the Gospel. This is one thing. Then we know that this grace of God was rare and little known under the Law; but that under the Gospel the gifts of the Spirit have been more abundantly poured forth, and that God has dealt more bountifully with his Church. But still the main thing is, to consider what the Law of itself is, and what is peculiar to the Gospel, especially when a comparison is made between the Law and the Gospel. For when this comparison ceases, this cannot be properly applied to the Law; but with regard to the Gospel it is said, that the Law is that of the letter, as it is called elsewhere, (Rom. 7:6) and this also is the reason why Paul calls it the letter in 2 Cor. 3:6, “the letter killeth,” etc. By “letter” he means not what Origen foolishly explained, for he perverted that passage as he did almost the whole Scripture: Paul does not mean there the simple and plain sense of the Law; for he calls it the letter for another reason, because it only sets before the eyes of men what is right, and sounds it also in their ears. And the word letter refers to what is written, as though he had said, The Law was written on stones, and was therefore a letter. But the Gospel — what is it? It is spirit, that is, God not only addresses his word to the ears of men and sets it before their eyes, but he also inwardly teaches their hearts and minds. This is then the solution of the question: the Prophet speaks of the Law in itself, as apart from the Gospel, for the Law then is dead and destitute of the Spirit of regeneration."