In the selection, Cardinal Ratzinger responds (orally---the book is a transcribed interview) to the following question. The fragments quoted by Zarabas above are bolded.
The patriarch Jacob had more or less described the time when this Redeemer would come, as in fact it was at the birth of Christ. Many had fallen away from the faith; Pharisees lived a life full of pride and lovelessness, as it says; the rest felt like a flock of sheep without a shepherd. The longing for the Master had grown equally great, both among Jews and among Gentiles. “Drop down the righteous, O heavens, from above!” pleads the prophet Isaiah, “and you, clouds, rain him down!” Yet nonetheless: Might it not be that these prophecies were fabricated in response to Jesus, and in fact only in retrospect?
The first sentence of your question refers to the so-called benediction of Jacob (Gen 49), which consists of a collection of promises, often quite mysterious, for the twelve sons of Jacob. In the blessing of Judah it says, “The rule shall not depart from Judah, nor the scepter from his feet, until the coming of the one to whom it belongs, to whom the obedience of all peoples is due” (49:10). That was then interpreted as a promise concerning the kingdom of David (David belonged to the tribe of Judah), and after this kingdom’s disappearance---in the time of Jesus, that is---as the promise of a new son of David, the Messiah, who would also command the obedience of all the peoples of the world, the non-Jews. It is obvious that Christians would see this promise as being fulfilled in Jesus the Son of David. But this text (scholars still disagree about its period of origin) does not go so far as to describe the time of Jesus, and its words point mysteriously to the future, and its meaning only seems clear in the light of Christ.
Now let’s take the prophet Isaiah. The original text in fact reads “Drop down righteousness, O heavens.” Only after righteousness had come in the guise of a particular person did the Christians read this text with a personalized reference. Thus in this relationship of agreement between Old and New Testaments we can see how the word of Scripture offers a progressive way. The words go to meet him; they seek him out where he is still in obscurity.
It is of course possible to read the Old Testament so that it is not directed toward Christ; it does not point quite unequivocally to Christ. And if Jews cannot see the promises as being fulfilled in him, this is not just ill will on their part, but genuinely because of the obscurity of the texts and the tension in the relationship between these texts and the figure of Jesus. Jesus brings a new meaning to these texts---yet it is he who first gives them their proper coherence and relevance and significance.
There are perfectly good reasons, then, for denying that the Old Testament refers to Christ and for saying, No, that is not what he said. And there are also good reasons for referring it to him---that is what the dispute between Jews and Christians is about. But this is not all. A great part of the purely historical and critical exegesis, likewise, does not read the Old Testament in this sense of pointing the way forward; it regards the Christian interpretation of it as being inconsistent with the original meaning, or at any rate as going far beyond it.
One would have to add this: The Old Testament is not an oracle; it is a path. We still have the freedom to reject it. I would say that the very fact that this freedom is open to us is a guarantee that the texts will stand on their own. It is quite clear that historically the Old Testament precedes Christ; the faith and the Scriptures of the Jews make that as clear as day. The Church Fathers saw it as the historical mission of the Jews that, by saying Yes to the Old Testament and No to Jesus, they give a universal guarantee of the age and authenticity of their sacred books. This, so the Fathers thought, was why they remained Jews and did not become Christians. The texts stand on their own, but they gain a new significance and unity of view when we read them with Christ.
God and the World: A Conversation with Peter Seewald. Ignatius Press, 2002, pp. 207-210.