Комментарий к Берешит 29:16

וללבן שתי בנות, the Torah interrupted Yaakov’s narrative by telling us that seeing that Lavan had only two daughters and the younger one appealed to Yaakov, he asked her father for her hand in marriage.

וללבן שתי בנות, And Laban had two daughters, etc. The Torah meant to inform us that both daughters were well known, the elder as Leah and the younger as Rachel so that Laban could not pretend afterwards that their names were different. Jacob stipulated that he would serve Laban for his smaller daughter Rachel in order to remove all possible doubt about whom he had in mind. When the Torah described Leah as גדולה, this was not a relative term, but she was tall in her own right not merely by comparison to Rachel, apart from the fact that she may have been a year or two older than her sister. Rachel too was of below average height not only because of her age.

וללבן שתי בנות, the fact that Lavan had two daughters, etc., is mentioned at the beginning of this paragraph in order for us to understand what is reported later about Yaakov having fallen in love with Rachel and offering to serve Lavan for 7 years for her hand in marriage. The Torah wants us to understand that Yaakov would never have agreed to work for Leah’s hand in marriage for even a fraction of such a long period.