Where did Yitzchok go?

Rabbi Yosef Karo remains one of the most important figures in the development of Halacha, practical Jewish Law. Less known, is the fact that he was also a significant Kabbalist. He was visited regularly by an angel who shared with him Torah insights. In the year 1585 on the night of the 22 of Cheshvan the angel shared the following with him:

Why does Parshat Toledot begin by saying "These are the happenings of Yitzchok the son of Avraham?" Don't we already know who Yitzchok's father is? Even more puzzling is the next phrase which says "Avraham begat Yitzchok." This seems to just be repeating the superfluous lineage that was anyway just mentioned.

By explanation the angel told him that the reason why Yitzcchok was unmarried at age 37 was because he represented din the spiritual force in the Universe which represents constriction and limitation. This is not a force which represents increase in the form of having offspring. The Akedat Yitzchok, the Binding of Yitzchok, was done in order to mitigate in some way the force of that din. Similar to the slaughtering of animals before they are eaten, which is done in order to remove the blood in them which represents din, so too, some of Yitzchok's blood had to be shed to minimize his din.

This was the miracle of the Akeida that God performed in order to enable Yitzchok to have offspring. At the moment Avraham drew blood from Yitzchok, the soul of Yitzchok left him, and at that moment Sarah's soul left her as well. Sarah, the life partner of Avraham, represented chesed, the spiritual force of abundance, the opposite of din. Her soul then united with that of Yitzchok to create a soul which combined the two forces, allowing him to father children.

Yitzchok then spent three years in Gan Eden recuperating from the injury inflicted on him.

These are the offspring of Yitzchok the son of Avraham; Yitzchok only ended up having offspring as he was the son of Avraham who represented Chesed. But it was necessary first for Avraham to beget Yitzchok an additional time before this could occur.