ואלה תולדות יצחק אברהם הוליד את יצחק  

And these are the descendants of Isaac, Abraham’s son.  Abraham fathered Isaac

Genesis 25:19

The Midrash Rabbah (Genesis 63:1) says:

It is written (Proverbs 23:24)  “גיל יגיל אבי צדיק ויולד חכם ישמח בו” (the father of the righteous will greatly rejoice, and he who begets a wise child will be glad in him). There is rejoicing upon rejoicing when a righteous child is born.

Our master explains that the term “righteous” (צדיק) refers to a child that is righteous from birth, the righteousness of a child at birth being attributable only to the holiness of his parents, while the term “wise” (חכם) refers to one elevated by his own knowledge and intellect, not by his genetic makeup. Thus, as explained elsewhere (“סדר נח “ונח איש צדיק היה בדורותיו), Noah was called “righteous” (צדיק) and Abraham “wise” (חכם).

From the passage “ויעתר לו” (and the Lord listened to his prayer), our Sages (Yevamot 64a), inferring that God listened only to Isaac’s prayer, not to Rebecca’s, concluded that the prayer of a righteous person that is the child of a righteous person (צדיק בן צדיק) is preferred to that of a righteous person that is the child of a wicked person (צדיק בן רשע). The Scripture, therefore, says “אברהם הוליד את יצחק” ) Abraham fathered Isaac (inasmuch as Isaac’s prayer for children was accepted only on account of being Abraham’s child, so that it was Abraham who enabled Isaac to be a father. 

The verse “גיל יגיל אבי צדיק ויולד חכם ישמח בו” quoted by the Midrash, refers to one who, having merited a righteous child (i.e., a child already destined at birth for holiness) must, to have been capable of fathering such a child, at least be wise. Such a father will rejoice twice — first for his own child, and second for the yet to be born grandchild, when his own child’s prayer for children (i.e., the prayer of a righteous person who is the son of righteous person) is accepted. But one whose offspring is called a wise child is himself neither righteous nor wise, because his child, like Rebecca, had to become righteous through his or her own efforts. For such an offspring, the father can rejoice for the child, but not for a yet to be born grandchild, because there is no assurance that his own child, not being the child of a righteous person, will merit to have his prayer for children accepted.

ויאמר הקול קול יעקב והידים ידי עשיו וכו’ ויברכהו

And he said: “The voice is Jacob’s voice, but the hands are the hands of Esau” . . . so he blessed him

Genesis 27:21-22

Our master explains that Rashi,’s comment that the words “הקול קול יעקב” (the voice is Jacob’s voice) mean that he spoke in a deferential tone – “קום נא” (arise, I beg you) – was necessary, because Jacob’s voice sounded like Esau’s. If his voice had not sounded like Esau’s, Jacob would have surely have expected Isaac to recognize who was speaking to him.

We know that Jacob fulfilled to the utmost degree the commandment to revere his father, always speaking to Isaac in a deferential tone. But he did not adequately fulfill the commandment to honor his father, for we know that he was punished for failing to do so. Esau acted in the opposite way, breaching the law and speaking to Isaac in a harsh tone, without appropriate reverence – “יקום אבי” (let my father arise). However, Esau, fulfilled the commandment to honor his father to his utmost, always bringing Isaac venison, so that the Sages (Bereshit Rabbah 65:1) understood the verse (Psalms 80:14) “יהרסמנה חזיר מיער” (The boar from the forest ravages it) as a reference to Esau, because, in his outward display of piety, he resembled a swine (which, flaunting its cloven hooves, seeks to appear as if it were a ritually pure animal). Thus, Esau treated his father generously, even as the Scripture says (Deuteronomy 15:8): “פתוח תפתח ידך לו” (you shall surely open your hand to him), which explains why he was his beloved to his father.

So when Jacob brought the savory meats loved by his father, Isaac perceived that not only was he fulfilling the commandment of honor, but was also speaking in a mild and respectful tone. Believing that Esau had now fulfilled both commandments (honor and reverence), Isaac felt that Esau now truly deserved to be blessed. So by saying “the voice is Jacob’s,” Isaac meant that he was being spoken to with the deference of Jacob, and by saying “and the hands are the hands of Esau,” he meant that he was being treated with the open-handed generosity of Esau. That is why Isaac blessed him.

ויחרד יצחק חרדה גדולה עד מאוד וכו’ גם ברוך יהיה

Then Isaac trembled violently and said, “Who was it then that hunted game and brought it to me, and I ate it all before you came, and I have blessed him? — yes, and he shall be blessed.”

Genesis 27:33

See Rashi and Ramban who both advanced forced explanations for the change in Isaac’s attitude:  at first fear and trembling and seething anger, and then whole-hearted reaffirmation of the blessing given to Jacob. The difficulty arises because Isaac said “בא אחיך במרמה” (thy brother came with guile), the word “מרמה” always indicating a transgression. Nevertheless, Rashi felt obliged to adopt a forced interpretation of “מרמה” as “חכמה” (cleverness).

So our master explains that this verse actually summarizes the entire incident. First, “ויחרד יצחק חרדה גדולה עד מאוד” (Isaac trembled violently), asking in the heat of anger “מי איפה הוא הצד ציד” (who, then, was it that hunted game?) until finally Isaac’s anger subsides, and he confirms the original blessing to the one by whom he had been deceived. The Scripture proceeds to recount each point separately, while explaining the reason for each as follows (Genesis 27:34-35): 

 כשמוע עשיו את דברי אביו ויצעק צעקה גדולה ומרה עד מאוד ויאמר ברכני גם אני אבי (When Esau heard the words of his father, he cried with a great and exceedingly bitter cry and he said, “Bless me, even me also, O my father!” And he said, “your brother came with cunning and has taken away your blessing.”)

These words of Isaac were spoken in anger. By saying “בא אחיך במרמה” (your brother came with cunning), Isaac meant that Jacob had committed an iniquity – a transgression — not that Jacob had been permissibly clever (בערמה). In saying this, Isaac wanted to reassure Esau that Jacob’s actions would not avail him at all, because Jacob, having acted deceptively, would not achieve his goal. But, feeling reassured, Esau responded aggressively (Id. 36), “הכי קרא שמו יעקב ויעקבני זה פעמיים את בכרתי לקח והנה עתה ברכתי” (Is he not rightly called Jacob? For he has supplanted me these two times. He took my birthright, and behold, now, he has taken away my blessing.) With these words, Esau poured salt on his own wounds, because Isaac’s anger toward Jacob was thereby abated, Isaac now understanding that Jacob, having previously acquired the birthright, was indeed the first-born, and therefore had taken the blessings by right. The Scripture therefore continues (Id. 37): “לך אפוא מה אעשה בני הן גביר שמתיו לך ואת כל אחיו נתתי לו לעבדים” (What, then, can I do for you, my son? Behold I have made him your lord, and all his brothers have I given to him for servants). So verses 34-37 were meant to explain and elaborate on the earlier passage in verse 33 from “ויחרד יצחק” (And Isaac trembled greatly) until “גם ברוך יהיה” (yes, and he shall be blessed).

One of our master’s students brought a clear proof to this interpretation from verse 34, which, instead of saying “ויהי כשמוע עשיו” (and it was when Esau heard) says “כשמוע עשיו” (when Esau heard), implying that the Scripture is recapitulating to explain what was said previously, not providing a narrative of further events. And this is very correct.