Related sobre Baba Metzia 7:15

(Translated from the Ehrfurt manuscript:) Any stipulation which has the action at the beginning, such a stipulation is invalid. How so? [If he, the brother-in-law whose brother died, said to her, his dead brother's wife,] "Now that I have released you from the levirate bond, with the understanding that my father is happy about it", even if his father doesn't want this—she is divorced [since he already released her with halitzah]. "Now that I have had sex with you, [be betrothed to me] with the understanding that my father is happy about it", even if his father doesn't want this—she is betrothed [since they already had sex, the stipulation is void]. Rabbi Shimon ben Yehudah says in the name of Rabbi Shimon: If the father wants it—she is betrothed, for she only had sex because of that original condition. Rabbi Shimon ben Elazar had a pneumonic: Any stipulation which is possible to do oneself or with an agent and he stipulated about it—his stipulation stands; but any stipulation that is impossible to do except with his body and he stipulated about it—his stipulation is void. How so? "Behold I divorce you with the understanding that my father is happy about it", if the father wants it—she is divorced; but if he doesn't want it—she is not divorced. "Behold I betroth you with the understanding that my father is happy about it", if the father wants it—she is betrothed; but if he doesn't want it—she is not betrothed.

Rabbi Yehudah says: [The husband] can always eat the fruits' fruit [i.e. the interest's interest, even if he said in the ketubah that he gives up access to the fruit from her property]. How so? He can sell the fruit and buy with [that money] land, and he can eat the fruit. Rabban Shimon ben Gamliel and Rabbi Yohanan ben Berokah say: If she dies, he inherits it [the fruit, even if he said he wouldn't have access to it in the ketubah], for she made a stipulation against what was written in the Torah and anyone who stipulates against what is written in the Torah, his stipulation is null and void.