This week's Torah portion (Vayetzei) tells how Jacob was deceived by Leah, or rather, by her father Laban who schemed to switch the girls at the wedding ceremony in order to retain the services of his nephew for another seven years. Jacob, who understood that his uncle was crooked, had previously given Rachel a password to identify her veiled presence to him at the wedding, but when she later realized that her father intended to have Leah take her place under the chuppah, quickly gave the password to her sister to save her from humiliation (Megillah 13b).
During the nuptial night, Leah responded whenever Jacob called her Rachel. When daylight came, Jacob discovered the deception and was angry. "O you deceiver, daughter of a deceiver, why did you answer me when I called Rachel's name?" Leah responded that she had learned such duplicity from him. After all, wasn't his deception of his father for a good cause? Likewise so was hers a good cause, since she wanted to be a mother of a righteous man (and not forced to marry Esau). Moreover, just as Jacob followed his mother's orders, so was Leah following her father's.
Jacob then confronted Laban, who assured him that he would be given Rachel as his wife as well, but only after the seven day period (i.e., the customary "sheva berachot") was ended, and only on the condition that Jacob would serve him for another seven years. After the bridal week ended, Jacob finally married Rachel and "loved her more than Leah" (Gen. 29:28-30). When God saw that Leah was "hated," he opened her womb to become the first matriarch of Israel (Gen. 29:31).
Did Jacob really "hate" Leah? The sages didn't think so. In comparison to Jacob's profound love for Rachel, however, it was as if he hated Leah in comparison. Recall that Jacob first agreed to serve Laban for seven years for the honor of Rachel's hand, which seemed to him "as a few days" (Gen. 29:20). But if Jacob loved her so much, wouldn't seven years seem like an interminably long time? The answer is that Rachel was so precious in his eyes that he considered the wait a small price to pay. Rachel was Jacob's deepest heart's desire -- and no one, not even her sister, could take her place....
A midrash states that Leah was hated not by Jacob but rather by the residents of the area. Everyone knew that she had "tricked Jacob" into marrying her, and therefore she was held in contempt. At any rate, Leah became the first mother of Israel, and the sibling rivalry (similar to that which Jacob experienced with Esau) was now underway.
It was prophesied that Jacob would bear twelve sons. The two sisters understood this and vied with each other to bear his children. Leah took an early "lead" in the race, bearing four sons, followed by Rachel's surrogate Bilhah (two sons) , followed by Leah's surrogate Zilpah (two sons), followed again by Leah, who bore two more sons. That equaled ten sons -- and still Rachel had not conceived. Finally, God opened Rachel's womb and Joseph was born, whom Jacob considered to be his "first born son." That made eleven, with one more son to go... According to midrash, Leah's seventh child was destined to be a son, but God changed the embryo to female on account of her prayers for Rachel (she didn't want to see her sister ashamed, so she prayed that she would be at least be equal to the handmaids who each bore Jacob two sons). This was fitting since, according to the sages, Rachel -- not Leah -- was the chief matriarch of Israel (if Jacob had not loved and worked for Rachel, he never would have married Leah in the first place). Indeed, Israel was later to be delivered by her firstborn Joseph and later was collectively called by the name of her grandson, Ephraim.
Rachel died while giving birth to Jacob's final son when the clan fled from Laban and returned to the Promised Land (Gen. 35:16-20). According to Rashi (and others), her death was unwittingly caused by Jacob's curse that whoever stole Laban's idols should die (Gen. 31:19-27). But why wasn't she buried in the Cave of Machpelah, only 20 miles away from Bethlehem? Because the prophet had foretold of her weeping for her children (Jer. 31:15), and Jacob had foreseen this.