We have learned that the only vows that a husband has the ability to nullify are nedarim that affect the personal relationship between husband and wife – bein ish le-ishto – or nedarim that are considered vows that make her suffer – innuy nefesh. How do we define innuy nefesh? The examples offered by the Tanna Kamma in the Mishna are vows that would keep a woman from bathing or perfuming herself, while Rabbi Yosei limits them only to cases where the woman would suffer some physical lack, like if she were to have to stop eating certain foods.
Our Gemara questions whether the inability to bathe should be considered innuy nefesh, since we find that on Yom Kippur – a day on which the Torah commands us to suffer innuy nefesh (see Vayikra 23:27) – only people who eat, drink or perform work will suffer the punishment of karet for desecrating the day. Since bathing, while forbidden, is not punishable, it would seem that it is not truly a situation of innuy nefesh. Rava answers that the Torah distinguishes between the requirement for immediate innuy nefesh on Yom Kippur and the long-term innuy nefesh implied in a neder. Innuy nefesh of Yom Kippur involves activities that cause suffering within a relatively short period of time, like eating and drinking. A person can go for a relatively short period of time without bathing and it will not create a situation of innuy nefesh. Over time, however, it certainly will create such a situation.
According to the Gemara in Massekhet Yoma (74b) the source for limiting the punishment of karet for innuy nefesh on Yom Kippur solely to eating and drinking, is based on the way the passages (Vayikra 23:29-31) read. We find that the term va-ha’avadeti et ha-nefesh is placed immediately after the stated punishment of karet, and this juxtaposition is understood to limit the punishment only to innuy nefesh that have the potential to lead to loss of life. Those include eating and drinking, but not bathing.