The Kesav Sofer says that Yaakov understood this distinction and he knew why the Torah prohibited a man from marrying two sisters—to prevent sibling rivalry. However, Yaakov knew that Rochel was such a big tzadekes that she would not fight with her sister. Therefore, he did not need to worry about the prohibition of marrying two sisters. Consequently, Yaakov was confident that the prohibition of marrying her sister did not apply in this case.
How did Yaakov know that Rochel was such a big tzadekes? Maybe Rochel would ultimately come to hate Leah? The fact that Rochel was so righteous that she gave her sister the secret code convinced Yaakov that Rochel was such a big tzadekes that there would not be sibling rivalry.
On the other hand, says the Kesav Sofer, maybe that was a momentary flash of greatness on Rochel’s part. Sometimes people can rise to the occasion once in a lifetime. Perhaps over the course of time, the natural feelings of resentment and strife between the two sisters would surface. Perhaps that is even why Rochel did not have children for all those years. What if Yaakov had been mistaken? If it would turn out that Rochel came to hate Leah, wouldn’t that retroactively prove that Rochel was in fact an ervah (i.e. – that the Torah’s prohibition of marrying two sisters did apply to her) and therefore Rochel’s children would have been mamzerim since she was an ervah to Yaakov?
Rochel finally did have children after Leah made that outrageous statement that “You stole my husband.” Rochel did not say a word in reaction. At that moment, it became clear that Rochel’s righteousness at the time of Leah’s marriage to Yaakov was not just a momentary thing. This was the essence of who Rochel was. Therefore, immediately after that, eight pasukim later, Rochel gave birth to her first child! Why now? Because it became clear that Rochel was such a tzadekes that she would never hate her sister in their co-wife relationship. Rochel would therefore never be an ervah to Yaakov, and her children with him would not be mamzerim.
The Kesav Sofer says that this also explains how Leah could make such a statement – because Rochel was so generous and non-resentful of what happened that Leah did not even think to consider the fact that Rochel did her a favor.
The Kesav Sofer’s approach answers several questions: It answers how Yaakov could marry two sisters. It answers why Rochel was barren for so many years. It answers how Leah could make the statement ‘Is it not enough that you took my husband?’ It answers how it was that Rochel was so passive in her response to Leah’s chutzpah. There is only one problem left:
Leah has six sons; the handmaidens each have two children. Why is it that Rochel only has two children like the handmaidens? This does not seem fair. Where is the reward for her kindness and tzidkus?
I saw in a sefer that it is fair. When someone goes to Eretz Yisroel, stop number one is the Kosel HaMa’aravi, but what is stop number two? It is Kever Rochel! Why? Everyone considers Rochel to be their mother! She may have only had two biological children but she became THE matriarch of Klal Yisroel. Out of all the Imahos, she is the prototypical mother of all of Klal Yisroel. When you have a problem, you cry to your mother. When you have a problem, you cry at Kever Rochel.
In spite of the fact that Hashem only gave Rochel two biological children, He saw to it that Klal Yisroel treats Rochel Imeinu like our true mother. The Ribbono Shel Olam does not let a good deed go unrewarded. Rochel’s acts of incredible selflessness were not merely a momentary thing. This was the ongoing essence of her character. For that she became Mama Rochel. (R’ Frand)
