The ketuba is one of the safeguards that the Sages developed for the protection of the interests of a married woman. Among the guarantees in a ketuba is a sum of money that the woman can collect (usually 100 or 200 zuz) in the event that her husband dies or divorces her. This obligation is guaranteed by land that he owns, and she will be able to collect her ketuba from that land if there is no money available to pay her otherwise.
Our Gemara quotes a Mishna in Massekhet Pe’a (3:7) that teaches that if a man divides his wealth between his children at the end of his lifetime and includes a portion of land for his wife, as well, then ibdah ketubatah – she has lost her ketuba.
The Gemara questions why she should lose her ketuba simply because she was given part of his wealth while he was alive. Three explanations are offered by the amora’im:
Rav suggests that she played a role in transferring the property to the children
Shmuel says that the case is one where she stood and watched the division of the property without objecting
Rabbi Yosei b’Rabbi Ḥanina says that it is when he gave her land and specified that it was payment for her ketuba.
It should be noted that even when the Gemara says ibdah ketubatah – she has lost her ketuba – it only means that she loses the guarantee of payment for her ketuba. The actual money that is owed to her remains, and should he get other money or property before his death, the estate would pay the obligation as written in the ketuba.
The Gemara concludes with Rav Naḥman’s ruling that none of these situations is necessary. In fact, since the husband put her on equal footing with the children in his wealth, she loses her ketuba. According to the Rashbam, this means that the honor he is giving to her in receiving a share of the inheritance leads her to give up her rights as guaranteed in the ketuba.