Yoma, Mishnah 5. In the previous Mishnah we discussed the way children are gradually trained to fast on Yom Kippur, and that below a certain age they do not fast at all. In our Mishnah we will discuss people who may find themselves in a situation of possible danger, and therefore cannot fast.
A pregnant woman who smelled food:
The Mishnah rules that a pregnant woman who smelled a certain food, and whose craving for it is so intense that medically, if she does not eat it, danger will arise for her and for the fetus - "ma'achilin osah ad shetashiv nafshah" - we feed her until she is restored, until her mind settles and she feels like herself again, for this is a matter of danger to her life and to the life of her child.
The Gemara teaches that this situation is handled in stages:
We whisper in her ear that today is Yom Kippur. Sometimes this whisper has a calming effect, and the craving passes.
If that does not help, then ideally - when it is possible - we feed her in measured amounts: less than the volume of a date of food, and less than a cheekful of liquid.
If it is clear that this approach will not help, or there is medical knowledge that it will not help, we feed her whatever is needed.
A sick person - according to experts:
The Mishnah continues: "ma'achilin oso al pi beki'in" - a sick person is fed based on the assessment of medical experts, who are able to determine that the person is in danger and needs to eat. There was a well-known cardiologist in St. Louis whom Rav Shach of the Ponevezh Yeshivah would call before every Yom Kippur to consult with him as to whether he should fast.
And what happens when there are no experts available? The Mishnah says: "im ein sham beki'in - ma'achilin oso al pi atzmo" - when no medical experts are available, we rely on the sick person's own sense of his condition and feed him according to what he believes he needs, until he says that he has had enough and needs no more.
"The heart knows its own bitterness":
The Gemara explains that the Mishnah can be understood as teaching a further leniency: even when there are experts, and available specialists determine that the sick person does not really need to eat, if the sick person himself insists against their advice that he does need to eat, it is as though there are no experts here at all, and we listen to the sick person. The basis for this is the verse in Mishlei: "The heart knows its own bitterness" - we rely on the person himself and feed him according to his words.
In summary: In this Mishnah we learned of two situations in which saving a life overrides the fast: a pregnant woman who smelled food, whom we feed until she is restored - first whispering in her ear, then ideally feeding her in measured amounts, and if that is not enough, whatever is needed; and a sick person, who is fed based on the assessment of experts, and in their absence according to his own sense until he says he has had enough. And we learned from the Gemara that even when experts are present, the sick person's own claim is decisive, for "the heart knows its own bitterness."