Yoma 83A

״זורו רשעים מרחם״. נפק מינה שבתאי אצר פירי.

“The wicked are estranged from the womb” (Psalms 58:4), i.e., it is clear they are estranged already in their mother’s womb. Indeed, Shabbetai the hoarder of fruits came out of her. He hoarded fruit during years of famine in order to inflate its price and profit at the expense of poor people.

חולה מאכילין אותו על פי בקיאין. אמר רבי ינאי: חולה אומר צריך, ורופא אומר אינו צריך ⁠— שומעין לחולה. מאי טעמא ⁠— ״לב יודע מרת נפשו״. פשיטא! מהו דתימא: רופא קים ליה טפי, קא משמע לן.

§ It was taught in the Mishnah: If a person is ill and requires food due to potential danger, one feeds him according to the advice of medical experts. R' Yannai said: If an ill person says he needs to eat, and a doctor says he does not need to eat, one listens to the ill person. What is the reason for this halakha? It is because the verse states: “The heart knows the bitterness of its soul” (Proverbs 14:10), meaning an ill person knows the intensity of his pain and weakness, and doctors cannot say otherwise. The Talmud asks: It is obvious that a person knows himself better than anyone else does. Why does this need to be stated explicitly? The Talmud answers: It is lest you say that the doctor is more certain because he has had more experience with this condition. Therefore, the verse teaches us that even so, it is the ill person who knows his own suffering better than anyone else.

רופא אומר צריך, וחולה אומר אינו צריך ⁠— שומעין לרופא. מאי טעמא ⁠— תונבא הוא דנקיט ליה.

However, in the opposite case, if a doctor says that the ill person needs food, but the ill person himself says he does not need to eat, one listens to the doctor. What is the reason for this halakha? It is because confusion [tunba] has taken hold of the ill person on account of his illness, and his judgment is impaired. Consequently, he himself does not know how much he needs food.