Accordingly, the third cup represents Rachel, and the fourth cup represents Leah.
This enlightens us as to the rationale for the sacred minhag to open the door after drinking the third cup representing Rachel Imeinu. We do so to evoke the merit of Rachel Imeinu who opened the door of her home so that Leah would not be embarrassed.
As the Gemara (Megillah 13b) explains, Yaakov Avinu was wary of Lavan’s duplicity and suspected that Lavan might substitute Leah in place of Rachel. Therefore, he gave Rachel signs, so that he would be sure he was with Rachel and not Leah. Despite his precautions, Lavan succeeded in inserting Leah in place of Rachel; and so that her sister would not be humiliated, Rachel gave Leah the prearranged signs,
On Account of Rachel HKB”H Will Mercifully Return Yisrael to Their Rightful Place
Following this line of reasoning, we will now explain the reason we open the door and recite "שפוך חמתך". According to the Midrash (Petichta D’Eichah Rabbah 24), at the time of the churban of the Beis HaMikdash, each of the holy Avos and Moshe Rabeinu came to weep and plead with HKB”H. He did not respond to them until Rachel Imeinu came and pierced the gates of heaven with her wailing. HKB”H responded to console her and give her moral support. It behooves us to present a translation of this moving passage from the Midrash as we approach this holy festival on which we pray for the geulah:
At that precise juncture, Rachel Imeinu rushed to HKB”H and said: Master of the Universe, it is known to You that Your servant Yaakov loved me deeply; he worked for my father seven years for my hand. When those seven years were completed, and the time arrived for me to marry my husband, my father planned to replace me to my husband with my sister. This was very difficult for me, because I was aware of his plan; I informed my husband, and I gave him a sign, so that he could distinguish between me and my sister, so that my father would not be able to replace me.
Afterwards, I consoled myself and endured my desire, because I had mercy on my sister, so that she would not be disgraced. So on the evening that my sister was substituted and given to my husband, I gave my sister all the signs that I had given to her husband, so that he would think she was Rachel . . . And I am but flesh and blood, dust and ash, I was not jealous of my surrogate, and I did not cause her to be humiliated and disgraced. And You, the King, the living and everlasting G-d, Who is merciful, why are you jealous of idol-worship, which is meaningless? And You exiled my children, and they were killed by the sword, and enemies did with them as they pleased.
The compassion of HKB”H was immediately aroused, and He said: For you, Rachel, I will return Yisrael to their place, as it is written (Yirmiyah 31, 14): “Thus said Hashem: A voice is heard on high, wailing, bitter weeping; Rachel weeps for her children; she refuses to be consoled for her children, for they are gone.” And it is written (ibid. 15): “Thus said Hashem: Restrain your voice from weeping and your eyes from tears; for there is reward for your accomplishment, etc.” And it is written (ibid. 16): “There is hope for your future—the word of Hashem—and your children will return to their border.”
This explains very nicely the rationale for the sacred minhag to open the door after drinking the third glass of wine, and to recite "שפוך חמתך" immediately afterwards. For, the third cup represents Rachel Imeinu, who opened her door to allow her sister Leah to take her place and gave her the prearranged signs, so that she would not be humiliated. In that merit, HKB”H assured her: “Restrain your voice from weeping and your eyes from tears; for there is reward for your accomplishment . . . And there is hope for your future—the word of Hashem—and your children will return to their border.” Hence, at that precise moment, we pray for the geulah from the galus of Edom in the merit of Rachel: "שפוך חמתך על הגוים אשר לא ידעוך"—pour out Your wrath upon the nations that do not acknowledge You.
