Nedarim, Chapter Ten, Mishnah Four
As we mentioned in yesterdays mishnah a father and husband jointly annul the vows of a betrothed girl who has not yet reached majority age. Furthermore, at this point the husband may annul vows that she took before she was betrothed. Once she is married, no one, neither her father nor her husband may annul the vows that she took before she was married.
Our mishnah relates what Torah scholars would do in order to avoid this problem.
It is the practice of scholars, before the daughter of one of them departs from him, he says to her, All the vows which you vowed in my house are annulled.
Likewise the husband, before she enters into his domain would say to her, All the vows which you vowed before you entered my domain are annulled, because once she enters into his domain he cannot annul them.
Evidently husbands in general and husbands who are Torah scholars (and hence understand the halakhot) in particular did not want to be surprised to find out that they had married a woman who was restricted by vows. Furthermore, a father would not want his daughter to be caught by her husband with previously made restrictive vows, for that may be grounds for divorce without payment of the ketubah (see Ketubot 7:7). Therefore, right before the girl would leave her fathers domain to enter her husbands domain, both the father and husband would annul vows that she had previously taken. Once she enters his domain, the husband would no longer be able to annul previously taken vows.
By the way, it seems likely that if we read between the lines of this mishnah, scholars married other scholars daughters. Rabbis formed a social class somewhat separate from other Jews and as a result, rabbis often married each others daughters.