1,540. Exchanging Rights for Responsibilities
Hilchos Ishus 12:4
The Sages instituted that a husband’s rights to the product of his wife’s labor corresponds to his obligation to sustain her; the obligation to redeem her corresponds to the right to benefit from her property, and the obligation to bury her corresponds to the right to inherit her kesubah. Therefore, a woman can opt to trade her husband’s obligation to feed her for his right to her work. He may not, however, forgo his right to work in exchange for not supporting her because perhaps his wife might not be able to support herself. Because of this enactment, supporting one’s wife is considered one of the conditions of the kesubah (even though the obligation to do so is of Biblical origin).
Hilchos Ishus 12:5
A husband is granted these four privileges and a woman is granted his ten obligations to her regardless of whether or not they were written into the kesubah, or even if no kesubah was written at all. They are automatic and need not be stated explicitly.