Chasidut su Genesi 21:12

Genesis ‎25,19 “And these are the generations of Yitzchok, the son ‎of Avraham; Avraham begot Yitzchok.” (We have been told in ‎Genesis 21,12 ‎כי ביצחק יקרא לך זרע‎, “for your seed (descendants) ‎will be known through Yitzchok.” G’d told Avraham already ‎before Yitzchok was born that although he had another son, ‎Yishmael, his descendants would always be associated with ‎Yitzchok. It was understood that this promise was contingent on ‎Yitzchok becoming a righteous person, a tzaddik, future ‎generations would not trace themselves back to their ancestor ‎Avraham but each generation would only trace itself back to their ‎immediate forbears, i.e. their fathers. In other words, the new ‎element provided by our verse above is that even Yitzchok’s ‎offspring would trace themselves back to their founding patriarch ‎Avraham. We learn from here also that it is up to the “son” to ‎demonstrate by his deeds that he was not only descended from ‎his father but could claim previous generations as his “roots.” ‎When we consider this, the word ‎תולדה‎ is no longer an adjective, ‎an attribute of a person which he came by naturally, without any ‎input of his own, but it is a tribute to the person so described, ‎meaning that he is a worthy descendant of his illustrious forbears.‎

Another way of looking at our verse is that of the ‎‎Ari’zal, who sees in the words ‎כי ביצחק‎ in Genesis 21,12 a ‎reference to the “feminine” side of Yitzchok in the diagram of the ‎‎10 emanations, i.e. the earthly element, seeing that the angel had ‎said to Avraham (Genesis 18,10) ‎והנה בן לשרה אשתך‎, “and here ‎your wife Sarah will have a son.” [The angel emphasized Sarah as ‎predominant in Yitzchok’s birth, not his father Avraham. Ed.] ‎However, subsequently he would receive a soul contributed by ‎Avraham, Avraham representing the masculine element of the ‎chart of the emanations. This point is made by the Torah here ‎repeating what otherwise would be assumed, that Avraham begot ‎Yitzchok. The Ari’zal’s comment also coincides with the ‎meaning of Bereshit Rabbah 58,5 in which the Midrash, ‎referring to Genesis 23,3 where Avraham is reported as “arriving” ‎in order to bury Sarah, asks: “where did Avraham arrive from? ‎Where had he been previously?” One of the answers given by the ‎Midrash is that Avraham came from Mount Moriah. The ‎‎Midrash adds that Sarah died as a result of the anguish she ‎experienced when told that Yitzchok had been slaughtered. She ‎had found this incompatible with G’d’s promise to Avraham that ‎ברך אברכך והרבה ארבה את זרעך‎, “I will continuously bless you and ‎greatly multiply your descendants” which G’d had said to ‎Avraham in Genesis 22,17.‎
At this point the author attributes to this Midrash a ‎third answer to the question whence Avraham came to arrange ‎Sarah’s funeral. I have not found this in any of my editions, ‎although this is the answer that would tie in with our verse ‎above. The Midrash supposedly views as Avraham “coming” ‎i.e. contributing the soul to Yitzchok as alluded to in the words ‎‎(Genesis 21,12) ‎כי ביצחק יקרא לך זרע‎.‎