The prohibition of a woman’s sister[1]
ואשה אל-אחתה לא תקח לצרר לגלות ערותה עליה בחייה
A woman, do not take her sister in marriage, to cause quarrelling, to reveal her nakedness upon her in her lifetime[2]
At the end of the parsha, we are taught a series of forbidden relationships, one of which is the prohibition of marrying one’s wife’s sister. However, the verse is expressed in a strange way. It says, “a woman, do not take her sister in marriage”. Now, the prohibition isn’t to marry any woman who is a sister. Only one’s wife’s sister. Why doesn’t it say don’t marry your wife’s sister? Or your sister-in-law?
Perhaps this is an allusion to an interesting teaching of our Sages[3]. In the World to Come, Hashem will make a feast for the righteous. The question will arise, who should lead the grace after meals, holding the cup of blessing? Avraham will decline, since he sired Yishmael. Yitzchak will decline, as he sired Eisav. Yaakov will decline, “for the Torah wrote for me, ‘A woman, do not take her sister in marriage’”[4]. What does Yaakov mean, that the Torah wrote for him? Isn’t the Torah written for everyone?
Now, Yaakov worked for Lavan in order to marry the latter’s daughter, Rochel. His whole goal and purpose was to marry her. In the end, Lavan tricked Yaakov and he ended up first marrying Leah, Rochel’s sister. Still, it’s clear that Rochel would be more likely called Yaakov’s wife, and Leah would be called his wife’s sister (and not vice-versa). It makes sense then why Yaakov would say that the Torah wrote for him “A woman, do not take her sister in marriage”. Meaning, he married Rochel second, and she’s the one who is called his wife. The prohibition of marrying her then couldn’t be referred to as “his wife’s sister”. Therefore, the Torah, when it wrote “A woman, do not take her sister in marriage”, was an allusion to Yaakov marrying Rochel.
Good Shabbos
[1] Based on Chanukas HaTorah parshas Acharei Mos § 117
[2] Leviticus 18:18
[3] Chanukas HaTorah cites this from Yoma 76 and Shemos Rabbah, parshas Bo, but we have it in Pesachim 119b
[4] We have no source which quotes Yaakov this way. Our version simply states that he married two sisters, which the Torah would eventually forbid