Parshas Toldos

Rivka tells Yaakov to bring her two goats to prepare for Yitzchak. Rashi explains that one was for the Korban Pesach and one was for the Chagiga.
Yitzchak had asked Esav to bring him some food from his hunting. Why didn't Yitzchak want a Korban Pesach? Why did Yitzchak ask for food in the first place? Why couldn't he give the Brocha without eating first?

Mefarshim explain that "Brocha" is overflowing, and you can only overflow if you are full.
The sense that all my needs are filled and I do not lack anything, allows Brocha to be given with a complete heart. This is what Yitzchak wanted to achieve. Rabeinu Bechayei compares it to Elisha hearing music in order to receive Ruach Hashem. But, he asks, in that case why didn't Yitzchak ask for music. He answers that the concept is similar to the Omer on Pesach where Hashem tells us to bring the grain that we wish to be blessed as an offering.
This idea could be understood as follows. What is the secret to having your grain blessed? Hashem says bring it as a Korban. Korban means that which brings you close. Take your first grain and bring it as a Korban and then Hashem will bless your crop. If you are going to use your grain as an agent to bring you close to Hashem, then of course He will give you an abundance. So too, if Esav uses his gifts and talents constructively, he will deserve Brocha. Rav Shimshon Rafael Hirsch explains that Yitzchak tells Esav to use his hunting skills to bring food to an old weak man, instead of just for sport and his own pleasure. By doing this, he makes himself deserving of Brocha.

The Malbim explains that Yitzchak wanted Yaakov to be like Shevet Levi. His descendents would be devoted to Avodas Hashem and Ruchnius. Esav's children would be like the rest of Yisrael who are responsible to support Levi's material needs.
So Yitzchak sends Esav on a mission to engage his skills as a hunter and forager in the service of others, so that he would receive a blessing that would equip him for the task Yitzchak envisioned for him. The Beracha of Ruchnius, Birkas Avraham was always meant for Yaakov. The Beracha meant for Esav makes no mention of Eretz Yisrael or Birkas Avraham.

Rivka knew that Yitzchak's vision of a nation composed of a partnership between Yaakov and Esav was not correct. She had the advantage of the Nevua she had heard during her pregnancy "Uleom Mileom Ye'ematz." The relationship between her sons would be antagonistic, and one would always dominate the other. When Yaakov is up, then Esav is down and vice versa. Yaakov must exist independently of Esav, and therefore needs to receive the material Berachos as well.

The mitzvah to take a lamb and slaughter it in Mitzrayim was a symbol of Bnei Yisrael conquering Mitzrayim and achieving independence at the expense of Mitzrayim's demise. (Ramban in Parshas Bo).
Yetzias Mitzrayim is the prototype for the ultimate Geula, when Bnei Yisrael will be redeemed from the Galus of Edom. That will also take the form of conquest, the destruction of Edom and independence of Yisrael emerging having taken the Koach of Malchus back from Bnei Esav. The Kli Yakar points out in his Perush on the Hagada, that the preferred choice for a Korban Pesach should be a lamb as lambs are mentioned first in the Pasuk. Also, the symbol of Mitzrayim was the lamb. Why were goats used predominantly for the Pesach in Bayis Sheni? He answers that Gedi is related to the word Hagada which is the mitzvah of the night. Perhaps we can suggest another answer. The lamb is the symbol of Mitzrayim, but the goat, Seir, is reminiscent of Esav. Esav is the Ish Sair. His land is called Seir. To impersonate him Yaakov covers himself with goat skins. In Bayis Sheni when we were under foreign domination, the symbolism of the Korban Pesach was twofold: It not only commemorated Yetzias Mitzrayim, but also foretold of the ultimate Geula in which the Seir will be slaughtered and we will defeat Esav.

Yitzchak who thought that Esav and Yaakov would be one nation, sharing this world and the next world, had no need for a Korban Pesach, as there would be no domination and no conquest. Rivka, who knew the truth, knew that the Korban Pesach was essential to the final outcome of the relationship between her children, so she prepares two goats. The Korban Chagiga is eaten for satisfaction. This achieves the intention of Yitzchak to tap the source of material Beracha which must now come to Yaakov. The second Goat is the Korban Pesach which symbolizes the ultimate victory of Yaakov.