ויקרא אליו ד' מן ההר לאמר כה תאמר לבית יעקב ותגיד לבני ישראל (19:3)
Sarah Schenirer immortalized our verse in coining the name "Bais Yaakov" for schools for girls. In referring to the men, the Torah uses the phrase the "sons" of Israel. Why when discussing the women does it use the phrase the "house" of Yaakov when "daughters" would seem to be the appropriate parallel?
Rav Meir Shapiro explains that when a person becomes ill, there are hypothetically two ways for a doctor to treat him. The standard procedure is to prescribe medication, although another theoretical option would be to design a room in which the air is saturated with the appropriate antibiotic. The first option has the drawbacks that it only helps one patient and requires active administration, whereas the latter could benefit many people without any effort on their parts.
Similarly, in fighting the universal illness known as the yetzer hara (evil inclination), men follow the prescription of the Gemora (Kiddushin 30b) to repel it through Torah study. Although the latter option isn't currently feasible for medical purposes, Jewish women nevertheless use it to ward off spiritual illness. As the backbones of the family, they imbue the entire home with an atmosphere of holiness and spirituality. This automatically benefits not only themselves, but also their husbands, children, and all who are fortunate to enter their homes.
This is alluded to in a well-known verse (Mishlei 1:8) שמע בני מוסר אביך ואל תטש תורת אמך – Listen my son to the rebuke of your father, and don't forsake the teachings of your mother. Shlomo HaMelech found it necessary to instruct a person to listen to the lessons of his father, while a mother's wisdom permeates the very air of her house and is absorbed without any effort. It is to teach and emphasize this idea that the Torah refers to the women not as the daughters of Yaakov but as the house of Yaakov.
taken from Parsha Potpourri (as usual)