Kabbalah su Genesi 25:19

"And these are the generations of Isaac, Abraham's son." Rabbi Yosi asks, What has changed? It did not say, "Abraham's son" previously. For although it is written, "Elohim blessed his son Isaac," (Gen. 25:11) Abraham is now dead; the image of Abraham was upon Isaac and stayed with him so that whoever saw Isaac said, "this is surely Abraham," and pronounced that Abraham begat Isaac.

"And Isaac was forty years old when he took Rivkah for a wife" (Gen. 25:20). Why is Yitzchak's age given here? Isaac was included within north and south, which are fire and water, and was then forty years old when he took Rivkah. Further, the text, "As the appearance of the bow" (Ezekiel 1:28), means green, white, and red. She (the Nukva) was three years old when he seized it, when he took Rivkah. And he sired a son when he was sixty so that he would properly sire Jacob who, as the issue of a man of sixty years, held on to all and became a whole man.

Midrash Ha'Ne'elam "And these are the generations of Isaac, Abraham's son, Abraham begot Isaac" (Gen. 25:19). Rabbi Yitzchak began the discussion with the verse: "The mandrakes give a fragrance..." (Shir Hashirim 7:14). The sages taught that in the future, the Holy One, blessed be He, will raise the dead and shake the dust off them. As a result, they will no longer be made of dust, as they were when first created from dust, which does not endure, as it is written, "And Hashem Elohim formed man of the dust of the ground" (Gen. 2:7).