Yoma 73b, 79a

Sitting next to my father, the rabbi, on the synagogue dais on Yom Kippur morning, I wondered how long I could last before breaking my fast. The lunch bag my mother gave me to bring to shul seemed to call out to me from the rabbi’s office where I had left it. By 10 a.m. I could stand it no longer. It was already three hours past my breakfast time. I felt the envious eyes of some worshippers follow me as I crept away toward the office.

Years later, I would come home from shul to visit my father, now ailing in bed on Yom Kippur. I would comfort him as he begrudgingly followed the doctor’s orders, eating just one small morsel of bread at a time, waiting 10 minutes, then eating another, waiting 10 minutes and then eating another. And I would tell him the same that he told me years ago as a child, “It’s OK, it’s a mitzvah for you to eat.”

Regarding Yom Kippur, the Torah states “ta’anu et nafshoteichem, you shall afflict your souls.” According to the interpretation of the Talmud, the words “ta’anu et nafshoteichem” mean that on Yom Kippur one may not eat, drink, bathe one’s body, wear leather shoes or engage in marital relations. The punishment for disregarding the prohibition against eating or drinking on Yom Kippur is karet, premature death at the hand of God. Disregarding the other prohibitions mentioned above is not punishable by karet, but is nevertheless prohibited.

Two conditions must exist, however, for the punishment of karet to apply to eating and drinking on Yom Kippur.

First, one must have eaten an amount of food equivalent to kotevet gasah, which means the size of a large date, or one must have drunk an amount of liquid equal to melo lugmav, which means a cheek full of fluid (between 32 and 40 grams).

Second, these quantities must have been eaten or drunk, as the case may be, within a period of time equivalent to kedei achilat peras, the time that it takes a person to eat half a loaf of bread. According to most opinions, this is equivalent to between eight to 10 minutes.

In the case of Yom Kippur, the Torah uses the term inui, affliction, and according to the Talmud, a person begins to feel the first signs of relief from hunger or thirst only after eating or drinking the above quantities. These quantities differ from the olive size or revi’it size (equivalent to the volume of one and a quarter eggs), which apply to non-kosher food or non-kosher drink or to chametz on Pesach.

A sick person who is told by a doctor, or feels him or herself, that refraining from eating and drinking on Yom Kippur will, or may, aggravate the sickness to the point of danger, is required by halacha to eat and drink on Yom Kippur. The halacha sees no merit in jeopardizing one’s health in order to fast on Yom Kippur. Quite the contrary, halachah roundly condemns such irresponsible behavior. “There is nothing virtuous about a sick person endangering himself. The Torah will hold such a person responsible for the harm he causes himself,” warns the Ramban.

The rule of thumb here is to follow the doctor’s instructions. In this case, the doctor decides. If the doctor or the patient is uncertain as to the effects of fasting on the health of the patient, one may take the following course of action. Preferably before Yom Kippur (but this may also be done on Yom Kippur, if one forgot) one should measure out quantities of food each equal to the volume of a large date, which according to Rabbi Ovadiah Yosef equals 30 grams. This can best be done by inserting the food into a measuring cup up to the 30-gram line.

The patient should eat this quantity of food on Yom Kippur and then wait about 10 minutes before eating the next same quantity and so on and so forth. Similarly, the patient should drink quantities of between 32 and 40 grams of fluid, waiting approximately five minutes between each sip.

If at any time the patient feels that he or she is well enough to lengthen the intervals or stop eating and drinking altogether without harm, one may do so. If, on the other hand, the patient or the patient’s doctor feels that the intervals should be shortened or that the patient needs to eat unrestricted amounts without any interruption, then the patient should do so. Any doubt in the matter must be resolved in favor of avoiding danger to the patient’s health rather than in favor of fasting.

A pregnant woman or a woman between the third and seventh day after birth may fast unless she feels faint, in which case one reminds her that today is Yom Kippur and if she still requests food, one offers it to her in the quantities described above until she recovers. A woman in labor, or within three days after birth, is not allowed to fast.

Food or drink taken through infusion is not considered eating or drinking for the purposes of Yom Kippur. Accordingly, a patient who is about to be detached from an infusion on Erev Yom Kippur, and who the doctor would allow to fast if the infusion remained attached, may fast with the help of the infusion. However, the infusion should not be inserted in the first place solely to enable one to fast.

Small children should not fast. However, according to some authorities, children between nine and 11 should, if they can, postpone their regular meal times by escalating amounts of one hour, two or three according to their age and strength. According to the Mechaber, a child of 11 may fast all day, but the Rema discourages this.

The sage Shammai was of the opinion that children should fast. But the rabbis disagreed and forced him to feed his children. Following the Musaf prayer, Rabbi Acha would announce in his synagogue that those with children should go home and feed them.

A person who eats on Yom Kippur for any of the reasons described above should recite Ya’ale Veyavo in Birkat Hamazon and Retzei if Yom Kippur is on Shabbat.

Raphael Grunfeld, a partner at the Wall Street law firm of Carter Ledyard & Milburn LLP, received smichah in Yoreh Yoreh from Mesivtha Tifereth Jerusalem of America and in Yadin Yadin from Rav Dovid Feinstein, zt’’l. This article is an extract from Raphael’s book “Ner Eyal: A Guide to Seder Nashim, Nezikin, Kodashim, Taharot and Zerayim” available for purchase at www.amazon.com/dp/057816731X  and “Ner Eyal: A Guide to the Laws of Shabbat and Festivals in Seder Moed” available for purchase at https://www.amazon.com/Eyal-Guide-Shabbat-Festivals-Seder/dp/0615118992. Questions for the author can be sent to [email protected].