As summarized by Channie Koplowitz Stein.
Much of the Torah, and by extension knowledge of our patriarchs and matriarchs, is revealed to us through the medrashim, the legend and lore that form the holy apocrypha to the text itself. Certainly this is the case in this parsha's episode of the marriages of Yaakov to Leah and Rachel. In fact, the light they shine illuminates not only the character of our Mother Rachel, but continues to illuminate the darkness of our long exile and provide hope.
The prophet Jeremiah encapsulates the greatness of Rachel, by quoting HaShem's response to her weeping as
What exactly did Rachel do and what was the essence of this deed that it had such a powerful effect?
Bnei Yisroel is led out in exile past her grave. While our other patriarchs and matriarchs, even Moses, beseeched God for His mercy, only Rachel received a positive response: "Keep your voice from weeping and your eyes from tears. For there is reward for your work... and they will return from the land of enemy. Yes, there is hope for your future... and children will return to their border."
This is the reward HaShem promises Rachel for "your work", yet we are left to question what exactly did Rachel do and what was the essence of this deed that it had such a powerful effect?
The Torah tells us that Yaakov's deal with Lavan was to work for him for seven years and then be given Rachel, Lavan's younger daughter, as a wife. Yaakov and Rachel were both well aware of Lavan's deceitfulness. Aside from the very detailed deal Yaakov made with Lavan, he and Rachel took precautions on their own and set up a code between themselves to assure that it was indeed Rachel under the marriage canopy. So how was it possible that Yaakov was tricked, in spite of all this planning?
Herein lies the greatness of our matriarch Rachel. Certainly, Leah could not have married Yaakov without both Rachel's consent and complicity. The medrash elucidates. Rachel, sensing her sister's impending humiliation at being rejected under the marriage canopy, reveals to her the secret signs and codes that Yaakov had taught her. Yaakov, therefore, is none the wiser until it is too late, in the morning, after the marriage with Leah is consummated.
This is truly a selfless act of ahavas chinom, love that is not rationally based, but rather based in the concern for one's fellow. What is so striking about this selflessness is that she may have thought that now her destiny and that of Leah would be reversed, that now she would marry Esau, as some commentators suggest. Even if she knew through prophetic revelation that she would still marry Yaakov, she now would become the second wife, a role she would have to live with for the rest of her life. As the first wife, she would have remained the soul mate to the spiritual essence of Yaakov, the future Yisroel. This role she relinquished to Leah, who became the mother of priests and teachers. Rachel's role now became to be the wife of Yaakov as he has absorbed the character of Esau. As such, she becomes the mother of Yosef, the one destined to be the provider and sustainer of the family through their sojourn in Egypt.
But Rachel has another son, Benjamin. By exploring his character and the essence of his descendants, Saul and Esther, much can be revealed about the enormity of Rachel's benevolence. Benjamin, we are told, knew that Yosef had been sold and not killed. Yet, for twenty one long years he did not reveal this secret. Saul, the first king of Israel, craved privacy and not publicity. When the prophet Samuel came to anoint him, Saul hid in the equipment room, eschewing public fanfare. Finally, Esther, the paradigm of discretion and silence, never told Ahashverosh, her husband and king, who she was and what nation she came from until Mordechai gave her permission to do so to save our nation.
This characteristic of discretion and silence came to Saul and Esther almost genetically. They learned it in their families not just by observing the actions, but by also observing the demeanor and continuing behavior after a chesed, an act of kindness, was performed. Yes, Rachel taught Leah the codes that would bind her and Yaakov together. And for the rest of her life, she lived with the reality that Leah was wife number one while she herself was wife number two. One incident that occurs seven years after their marriages proves highly enlightening.
Reuben, the firstborn child, is playing in the field. He runs to his mother, Leah, to present her with a bouquet of freshly picked mandrake flowers. Childless Rachel, sitting alongside her sister, sees the flowers of fertility and asks Leah for some of the flowers her nephew had brought. Leah's answer is enigmatic, to say the least, and perhaps even cruel. At the very least, it appears to be insensitive, given the great chesed that Rachel had done for her by facilitating her marriage to Yaakov.
Leah answers, "Was your taking my husband insignificant? And now to take even my son's dudaim?"
How does Rachel reply to this taunt? Does she throw it back at Leah to make Leah feel beholden to her? On the contrary, Rachel seems to be agreeing that Leah should always have been Yaakov's wife.
Only after this incident did HaShem remember Rachel and allow her to conceive. Here was proof positive that Rachel's selfless act was truly selfless. The Lev Shalem concludes that, although Rachel gave Leah the signs, she never told her that this was a code between herself and Yaakov. In essence, the signs were the manual for being a good Jewish wife, the laws of ritual impurity, the laws of separating challah and the laws of lighting Sabbath candles. As far as Leah knew, Rachel was teaching her how to be a Jewish wife, not giving away the secrets that could now seal her own fate.
During all this time, even during the seven years of courtship when gifts meant for Rachel found their way, through Lavan, to Leah, Rachel never revealed that she was Yaakov's intended. Now, Leah's comment about taking her husband makes perfect sense.
But let us examine Rachel's reply and plumb the hidden depths of her character. Rachel could easily have said, "You ingrate! Do you know what I did for you?" Instead, it is obvious that Leah does not know what Rachel did for her. In all this time, Rachel never made Leah feel inferior. Instead, she treated her sister as akeret habayit, "the mainstay of the house". Even at this moment, she was not going to drop the pose. Instead, she would retain this secret, and she answered Leah by acknowledging Leah's right to Yaakov, asking for this favor, and giving something important in return. Rachel did not do chesed, she was chesed personified.
The Thirteen Attributes of Hakodosh Boruch Hu include the phrase, verav chesed v'emes, "abundant in kindness and truth." It would appear that kindness and truth are mutually exclusive. If one is judged strictly by the standards of truth, then one does not merit kindness; and if one received kindness, then it is in spite of his not meriting this kindness. But HaShem has made a different calculation. Only He can supply opportunities for 
By taking the opportunity for chesed whenever it knocks, we are increasing our merits.
chesed that can then transform the negative din, "judgment", to positive results and blessings. By taking the opportunity for chesed whenever it knocks, we are increasing our merits so that even with pure judgment and truth we are now worthy of HaShem's blessings.
The beauty of Rachel was that she took these opportunities for chesed and used them throughout her life. Her chesed was done privately; no one except she and HaShem knew what she had done. Therefore, when Rachel now validates Leah's position and effaces her own role, HaShem remembers her and gives her a son. More than ever, she merited this loving kindness from HaShem.
This, indeed, is the lesson for us all. The Second Holy Temple was destroyed due to unfounded hatred among the Jews. HaShem listens to the voices of those who cry out to Him. He will especially listen to the voices of those who cry out to Him for others; and in the merit of this undeserved love we display for each other, in the confines of our own homes and the privacy of our own silent prayer, may He bring the full redemption soon, in our day, and may Rachel's children return to their border.