Ketubot, Chapter Eight, Mishnah Eight
This mishnah is a continuation of yesterdays mishnah, in which we learned that the widow has a lien on the dead brothers property. The yavam cannot even pay off her ketubah and then use this property.
1) He cannot say to her, Behold your ketubah lies on the table, rather all of his property has on it a lien from her kethubah.
2) So too, a man may not say to his wife, behold your ketubah lies on the table, but all of his property has on it a lien from her ketubah.
a) If he divorced her she is entitled only to her ketubah.
b) If he remarried her she is like all other wives, and is entitled only to her ketubah.
Section one: The yavam cannot say to his yevamah that he has designated for her a specific piece of property for her ketubah and that he therefore can do what he pleases with the remainder of his brothers property. Rather he cannot sell any of his brothers property.
Section two: Similarly a man may not set aside a certain piece of property and designate it for his wifes ketubah. When Shimon ben Shetach established the rabbinic ketubah, part or perhaps all of his legal innovation, was that all of a mans property is subject to his wifes ketubah. This is not to say that a man cannot sell his own property. However, if he does, and then when the wife comes to collect her ketubah her husband or his estate cannot pay it off, she can reclaim the previously sold property from its purchasers.
Section three: If the yavam divorces his yevamah, he can now pay off her ketubah and then sell the rest of the brothers property. If he remarries her, she no longer has the status of a yevamah, but rather she is like all other wives, who cannot prevent their husbands from selling their property.