daf bit: Bava Batra 123

[cellio]

In the midst of a discussion about inheritance and specifically the birthright (the double portion due to the first-born son), the g'mara discusses Yaakov taking the birthright away from Reuven and giving it to Yosef. Taking it from Rueven is explained (he sinned against his father), but why is Yosef entitled? (He's not the second-oldest.)
Because the birthright should have come through Rachel, the originally-betrothed wife, and not Leah, and Yosef is the firstborn of Rachel.

The g'mara then turns to Leah. The torah says her eyes were weak -- is it conceivable that the torah would speak disparagingly of her? No, Rav says, her eyes were weak, but this is no disgrace but a credit. You see, she heard people say: Rivkah has two sons and Lavan has two daughters, so the older son should marry the older daughter and the younger should marry the younger. So Leah (the elder daughter) inquired -- how does the older son conduct himself? He is a wicked man, a highway robber. And the younger? He is a quiet man dwelling in tents (meaning he is studious). And when she heard this she cried until her eyelashes dropped from her lids (which apparently caused her eyes to become weak). And when the Holy One, blessed be He, saw that Eisav's conduct was hateful to her, he opened her womb for Yaakov. (123a)