Aside from the personal relationship that is created between husband and wife at the time of their marriage, the marriage agreement involves agreement between them in other areas, as well. The economic union that the marriage creates is largely open to definition between the two parties. Thus, for example, the husband can choose to concede some of the obligations that his wife has towards him. Ha-kotev le-ishto, the ninth chapter in Ketubot, which begins on our, deals primarily with two such concessions. The first is a situation where the husband agrees to concede – entirely or partially – his rights to derive benefit from his wife’s property. The second is when he agrees not to demand an oath from her should she demand payment of her ketubah.
Much of the discussion in the Gemara is about the language that the husband uses when offering the concession to his wife. The Mishna teaches that saying, “I have no legal dealings or involvement with your property” – din u’devarim ein li be-nikhasayikh – will effectively allow her to sell the property, even though he will retain his rights to inheriting the property and continuing to benefit from it during her lifetime as long as she owns it. The Mishna explains that he would have to be more specific if he wants to remove himself from those rights to her property.
Regarding the specific language used, our Gemara quotes a that teaches that if someone says “I have no concern in this field and I entirely dissociate myself from it,” his statement is of no effect. The implication of this is that these statements have no legal validity because they do not clearly express the man’s intent; Tosafot says that it is lashon geru’ah – it is a poor expression. The rishonim point out, however, that there are cases where statements such as these are viewed as being significant. Specifically, we rule that someone who says one of these things to his non-Jewish slave successfully sets him free.
Rabbeinu Tam explains that we must distinguish between a field and a slave. The slave is able to take possession of himself, and as such, a statement that releases him from the owner’s control effectively releases him. A field cannot own itself, so a statement that is not clear enough will have no effect.