Vayetze 

ויצא

The Torah portion tells of Laban’s act of deceit, in which he promised his daughter Rachel to Jacob but then substituted Leah. The Sages relate that Rachel knew about the plan and acted with magnanimity to avoid her sister’s humiliation. 

Upon meeting Rachel, “Jacob told Rachel that he was her father’s brother” (Genesis 29:31). Was Jacob in fact her father’s brother? Wasn’t he the son of her father’s sister Rebecca? He was not her father’s brother, but when Jacob said to Rachel: Will you marry me? She said to him: Yes, but my father is a man of deceit, and you will not prevail against him. Jacob said to her: I am his brother, [I can contend with him,] in deceit. Rachel said to him: Is it permitted for the righteous to engage in deceit? Jacob said to her: Yes, as the verse teaches, “With the scoundrel act like a scoundrel, and with the perverse act perversely” (II Samuel 22:27). Jacob said to her: What is his method of deceit? Rachel said to him: I have a sister who is older than I, and he will not marry me off before she is married. Jacob gave her signs to prove her identity to him at their wedding. When the night arrived, Rachel said to herself: Now my sister will be shamed. Rachel gave the signs to Leah, and that is what is written: “It was in the morning and, behold, she was Leah” (Genesis 29:25). Is that to say that until now she was not Leah? The explanation is that because of the signs that Rachel gave to Leah, Jacob did not know until now, when the sun rose and he could see her, that he was with Leah. Therefore, due to her magnanimity, Rachel was rewarded, and Saul the first king of Israel came from her. [The verse relates that later, Rachel also married Jacob.] “God remembered Rachel, and God heeded her, and He opened her womb” (30:22) after a period of barrenness. Which memory did God remember for her? God remembered her silence for her sister at the moment that they were giving Leah to Jacob in marriage. She knew and she was silent. <source>(Megilla 13b; Bereshit Rabba 73) </source>