Bava Batra — Daf 49b

נחלה הבאה לו לאדם ממקום אחר אדם מתנה עליה שלא יירשנה וכדרבא דאמר רבא כל האומר אי אפשי בתקנת חכמים כגון זאת שומעין לו

מאי כגון זאת כדרב הונא אמר רב דאמר רב הונא אמר רב יכולה אשה שתאמר לבעלה איני ניזונת ואיני עושה

הא ראיה יש תימא נחת רוח עשיתי לבעלי

מי לא תנן לקח מן האיש וחזר ולקח מן האשה מקחו בטל אלמא אמרה נחת רוח עשיתי לבעלי הכא נמי תימא נחת רוח עשיתי לבעלי

הא איתמר עלה אמר רבה בר רב הונא לא נצרכה אלא באותן שלש שדות אחת שכתב לה בכתובתה

that a man is at liberty to renounce beforehand  an inheritance which is likely to accrue to him from another place;  and this rule again is based on the dictum of Raba, that if anyone says, I do not desire to avail myself of a regulation of the Rabbis of this kind, we comply with his desire.  To what was Raba referring  when he said 'of this kind'? — He was referring to the statement made by R. Huna in the name of Rab: A woman is at liberty to say to her husband, You need not keep me and I will not work for you. [Since the Mishnah says that a husband has no hazakah in the property of his wife, we infer that] if he has proof [that she sold it to him],  the sale is effective. [Yet why should this be?] Cannot she say [in this case also], I merely wished to oblige my husband?  Have we not learnt: If a man buys [a field] from the husband  and then buys it again from the wife, the purchase [from the wife] Is void?  This shows that she can say: I merely consented in order to oblige my husband, and cannot she say here also that she merely wished to oblige her husband? — The truth is that this [Mishnah] has been qualified by the gloss of Rabbah son of R. Huna: The rule really required to be stated in reference to those three fields [that are specially allotted to her]  — one that the husband inserted In the kethubah,