Why Isaac named Jacob as his heir and not his first-born son, Esau? Genesis attempts to justify this in two different ways; first, by accusing Esau of having sold his birthright for a dish of lentil stew, and secondly by suggesting that Jacob “tricked” Isaac into giving him the blessing. Neither of these theories is very convincing.
We have to consider that everything we know regarding the Patriarchs was at first passed on orally until someone, about the time of Moses, gathered these oral traditions and set them down in writing. But in all that time, the deeds of the ancients were narrated by the elders to an audience composed of relatives, their children, and servants. This would be a very attentive audience, anxious to learn about its origins. But when the narrator came to the key point of his story, that is, Isaac’s investiture of Jacob, we can imagine his embarrassment. There were undoubtedly some first-born sons in the audience, perhaps even some twins, who would be extremely attentive to this question: “Why Jacob, if Esau was the first-born?” Upon the answer to this question hung the legality of the primacy of Israel with respect to Edom. In those times this was by no means a question of secondary importance.
The two stories, one concerning the birthright sold for a dish of lentils, the other regarding the deception worked out by Rebekah and Jacob to the detriment of Esau, are ingenuous tales; they seem to have been concocted by two old people with no imagination, in order to dampen the curiosity of youngsters with no mature critical capacity.
These two stories are the kind to stir the imagination, especially in the case of a young boy, making them difficult to forget. This is proven by the fact that the “dish of lentils” has become a part of idiomatic expressions all over the world. Once narrated, even jokingly, they became traditional, passed on from father to son; two centuries later they were history. If the question is asked, whether there is any truth in them, the answer is certainly yes, there is; the storyteller must have based them on events that really happened, i.e. perhaps a comment by Esau, joking about the goodness of a dish of lentil stew, a ruse created for fun, and other possibilities such as these. They were quite banal incidents, common among brothers and
without any real importance, which the narrator, cornered by an insistent audience, whose curiosity had been aroused, had transformed into a circumstance which changed the course of History.
Neither story, however, can stand up to serious scrutiny. The episode of Esau selling his birthright for a dish of lentil stew can be discarded completely. If he had conducted himself in such a manner, Isaac would have had no reason to “bless” him instead of Jacob, who consequently would have had no need to resort to subterfuge. And, Esau would have had no reason to make accusations and to threaten vengeance. If Isaac really intended to “bless” Esau, it would indicate that his birthright was intact. The second episode, therefore, precludes the first one.
This second one can be discarded by a thorough investigation of the facts. First of all we have ascertained that Isaac was not very old when he gave his “blessing,” being only about fifty-four. Certainly he was ill, perhaps even seriously so. His decision to bring one of his sons into his affairs, was an indication that he foresaw, or feared, that he might not live much longer. Thus it was ill-health that caused him to make his testament. But it had to be his wife Rebekah who made him decide in favor of one son or the other.
The real reason Isaac disinherited Esau is to be found in Genesis 26, 34-35: “When Esau was forty years old he married Judith, daughter of Beeri the Hittite, and also Basemath, daughter of Elon the Hittite. They were a source of grief to Isaac and Rebekah.” Again, in Genesis 27, 46-28, 4: “Then Rebekah said to Isaac, 'I'm disgusted with living, because of these Hittite women. If Jacob takes a wife from among the women of this land, from Hittite women like these, my life will not be worth living.' So Isaac called for Jacob and blessed him and commanded him: 'Do not marry a Canaanite woman. Go at once to Mesopotamia, to the house of Bethuel, your mother's father. Take a wife for yourself there, from among the daughters of Laban, your mother's brother. May Almighty God bless you (...) may he give you and your descendants the blessing given to Abraham, so that you may take possession of the land where you live as an alien, the land God gave to Abraham.’”
The reason for Esau's loss of inheritance, therefore, is to be sought in his mother's opposition. He gave her an excellent excuse for favoring Jacob, by marrying not one, but two Hittite women. This may seem a rather banal reason for her action, but it presumes a rebellious character in Esau; his parents undoubtedly tried to dissuade him from marrying them, but he would not listen. Such disobedience was in itself a sufficient reason. It should also not be forgotten that Jacob had disinherited no less than three of his sons for similar reasons: Reuben for having raped his concubine Bilha, and Simeon and Levi for their violent nature, which led them to destroy Shechem (Gen 49, 3-7).
Furthermore, the prevailing view in those times held that the legal heir should be born of a marriage between blood relations; it was not without reason that Esau hurried to repair the damage by marrying his uncle Ishmael’s daughter. In his heart Isaac preferred his proud and impetuous son Esau, but evidently Rebekah knew how to use her womanly wiles to get her own way. So with the excuse of the Hittite marriages, she managed to convince her husband to disinherit Esau in favor of Jacob. Once the decision was made, Isaac called Jacob, blessed him and gave him the investiture, that is, the right to succeed him; but he made it a condition that Jacob choose a wife from among the daughters of his uncle Laban.
Jacob's decision to give the birthright to his fourth son Judah (Gen 49,8) does not appear to have caused any upheaval, perhaps because those excluded were three, whereas nine younger brothers were grouped on the other side. Esau, on the other hand, did not readily accept his father's decision. Perhaps he did not consider that he had done anything so bad as to merit such a punishment. He probably attributed his bad luck to a plot devised by his brother. As might be expected, he began to hate his brother and to brood over thoughts of revenge. Rebekah may have had a plan to neutralize her elder son and to consolidate Jacob's position, but Isaac's death came too suddenly, before she could put it into practice.
Thus it was that Esau managed to get the upper hand, forcing Jacob to flee from Palestine and to remain in exile for twenty years.