What is the significance that the younger one was holding on to the heel of the older one?
Rashi #1: Strictly speaking, the younger one ought to have been the Bechor, since he was formed from the drop that went in first. 1 So he wanted to be born first just as he was conceived first.
Rashi #2: It was a sign that the one would not complete his reign, before the other one came to snatch it away from him.
Moshav Zekenim #1: Esav is compared to a pig. Its Siman of Taharah is its heel (split hooves).
Moshav Zekenim #2: Yaakov had mercy on his mother. Once the womb opened, he held on to leave, lest the womb need to open a second time.
Yalkut Shimoni: A bishop asked Raban Gamliel who was destined to rule after them (Rome); R. Gamliel brought a clean piece of parchment and cited this Pasuk, "v'Acharei-Chen Yatza Achiv, v'Yado Ochezes ba'Akev Esav" - a clear indication that, at the end of time, Yaakov will take over from Esav.
Malbim #1: They will always be connected - when this one rises, this one falls.
Malbim #2: Yaakov is happy with matters that Esav tramples with his heel.
Malbim #3: The seed of Yaakov will be subjugated many days under the heels of the seed of Esav.
Malbim #4: The true reign of Yaakov will be when the kingdom of Esav is finished.
Ha'amek Davar #1: If there will be exile, Yaakov prefers to be under Esav (Gitin 17a).
Ha'amek Davar #2: This is like one who holds back another; when Esav will be at his peak, Yaakov will prevent him from getting stronger.
Rashi: This is like two stones that are pushed into a narrow tube - the one that entered first emerges last. Gur Aryeh - Rashi was bothered as to why Yaakov emerged second. (He ought to have been first (and he then would have received the Bechorah uncontested! - EK). He explains that Yaakov had been conceived first; therefore he emerged last.
What is the symbolism of grabbing hold of the heel?
Maharal (Gevuros Hashem Ch. 18, p. 82): When an old Tzurah 1 fades away, there is room for a new one to take its place. [So too, in a general sense, when evil is negated, the good is revealed]. Similarly, Chazal wrote that Mashi'ach is waiting - in the city of Rome! This is alluded to by Yaakov "holding onto" the heel (the end) of Esav.
In Maharal's expression, Tzurah means the purpose or actualization, which Chomer (raw material, raw potential) assumes. One Chomer cannot take on two Tzuros at the same time.
Bearing in mind that here, the word "va'Yikra" is in the singular, who called him 'Yaakov'?
Rashi #2: His father Yitzchak called him Yaakov. 3
Moshav Zekenim: He said, 'you named your pig; I will name My Bechor!' But a Midrash says that of the Avos, only Yitzchak's name was not changed, for HaSh-m Himself named him! It means that only regarding Yitzchak, HaSh-m called his name before he was born. Ohr ha'Chayim - If Yitzchak named him, it would not say "v'Yitzchak ben Shishim," rather, 'v'Hu....'
This serves as a sign that Yaakov will prevail in the end (Seforno).
See also Ba'al ha'Turim.
What is the significance that Yitzchak was 60 when they were born ?
Rashi: This was 20 years after he married. He waited ten years until Rivkah turned 13 and was able to bear children, and another ten years, until it became clear that she was barren, and then prayed for her. 1
Malbim: This is lest we say that Esav was red because his father was still in his hot-blooded youth.
Gur Aryeh (to 26:34): The number 60 represents wholeness, ten times the six directions (including up and down). Yitzchak fathered children when he reached wholeness, which was appropriate for his trait of Din. 2
Why did Yitzchak not marry a Shifchah like his father did?
Rashi: Because he became sanctified on Har ha'Moriyah as an Olah Temimah, and he did not want to defile that Kedushah by marrying a Shifchah.
QUESTIONS ON RASHI
Rashi writes: "[Yaakov] was holding him back, ... the last to enter is the first to emerge." On a deeper level, why did Esav emerge first?
Gur Aryeh (to 25:22): Esav was born first, for he was closer to this world of degradation and shame. Yaakov, who was unsullied, and closer to the world-to-come, was born last.
Maharal (Gevuros Hashem Ch. 67, p. 311): Had Yaakov been first, some of his own offspring would be unworthy (as was the case for Avraham and Yitzchak). 1 Therefore Esav emerged first, leaving Yaakov refined and purified.
Maharal: In creation, we rarely find perfection, rather various levels of greatness or deficiency.
Rashi writes: "Yaakov had been conceived from the first drop (of seed), and Esav from the second." What are the implications of this?
Maharal (Gevuros Hashem Ch. 29, p. 113): Yaakov was the Alul Rishon, the initial result (and primary goal), except that in this material world, he was revealed last in practice. 1 When they grew up, Yaakov purchased the Bechorah that was meant for him.
Rashi writes: "One (i.e. Esav) would not have the chance to conclude his reign, before the other (Yaakov) would arise and take it from him." How was this symbolized in this event?
Gur Aryeh: Grabbing hold while still in the womb symbolizes that Yaakov's rule would begin to emerge even before Esav reached the pinnacle of his greatness. Grabbing by the hand alludes to taking by force, and the heel alludes to the end (of Esav's reign).
Rashi writes: "And he called his name Yaakov - HaSh-m [did]; alternatively, it was his father (Yitzchak)...." In the preceding verse, Rashi also interprets the phrase, "they called his name Esav" (25:25). But one of these must be the usual expression; how can he make a derivation from both of them?
Gur Aryeh #1 (citing the author of Terumas ha'Deshen): We would have expected the terms to be reversed! Esav should have been named by his father, for the derivation was not as obvious; whereas everyone knew about Yaakov holding onto the heel. Rashi therefore explains that HaSh-m named Yaakov. Alternatively, Yitzchak hurried to name him Yaakov (meaning that he would ultimately take sovereignty from his brother), before someone else would give a different name.
Gur Aryeh #2: After using the pronoun "they" regarding Esav, our verse should have gone back to writing explicitly, 'Yitzchak named him.' Rashi answers that the 'Nistar' sense (lit. hidden, i.e. the third person pronoun 'he') alludes to HaSh-m. Alternatively, it must have been Yitzchak. The Torah need not explain this, for usually it is the parent who names a child, and none other.
Rashi writes: "Alternatively, it was his father (Yitzchak) who named him Yaakov, due to his holding the heel." Why did Rashi explain the derivation of Yaakov's name, only in this second approach?
Gur Aryeh: In the first explanation, HaSh-m gave the name Yaakov for the future, because his reign would come in the end [like the heel is at the end of the body]. Only regarding Yitzchak's naming of Yaakov must we explain that he was named for holding the heel, in the present.
Rashi writes: "[Yitzchak] did not wish to marry a maidservant (as his father did), for he had been sanctified as a burnt-offering." Why didn't he marry a second (full) wife, as Yaakov later would?
Gur Aryeh: After all of the miracles that HaSh-m had done for Eliezer to bring Rivkah to him (Bereishis 24), Yitzchak knew that she was his destined match from HaSh-m, and no one else. Taking a maidservant would not have gone against HaSh-m's decree, as she would be under Rivkah's domain. He refrained only because he had been sanctified at the Akeidah.
Rashi writes that Yitzchak prayed for Rivkah only after 20 years. Why did he wait? A Tzadik prays for everything that he lacks, and one who does not pray, does not get it (Gur Aryeh to 30:3)!
Divrei David: He prayed for himself before this. He did not know that she was barren until 20 years, and then he prayed also that she be cured.
Perhaps he prayed even before this. Rashi means that after 20 years, "va'Ye'tar" (he prayed very intensely - PF).