Mishnah Yoma 8:9

On Yom Kippur, the day on which there is a mitzva by Torah law to afflict oneself, it is prohibited to engage in eating and in drinking, and in bathing, and in smearing oil on one’s body, and in wearing shoes, and in conjugal relations. However, the king, in deference to his eminence, and a new bride within thirty days of her marriage, who wishes to look especially attractive at the beginning of her relationship with her husband, may wash their faces on Yom Kippur. A woman after childbirth, who is suffering, may wear shoes because going barefoot causes her pain. This is the statement of Rabbi Eliezer. The Rabbis prohibit these activities for a king, a new bride, and a woman after childbirth.

The mishna elaborates: One who eats a large date-bulk of food, equivalent to a date and its pit, or who drinks a cheekful of liquid on Yom Kippur is liable to receive the punishment of karet for failing to fulfill the mitzva to afflict oneself on Yom Kippur. All foods that one eats join together to constitute a date-bulk; and all liquids that one drinks join together to constitute a cheekful. However, if one eats and drinks, the food and beverage do not join together to constitute a measure that determines liability, as each is measured separately.

If one ate and drank unwittingly within one lapse of awareness, e.g., he forgot that it is Yom Kippur, he is liable to bring only one sin-offering. However, if he ate and performed labor unwittingly, he is liable to bring two sin-offerings, as by doing so he violated two separate prohibitions. If he ate foods that are not fit for eating, or drank liquids that are not fit for drinking, or drank fish brine or the briny liquid in which fish are pickled, he is exempt, as that is not the typical manner of eating or drinking.

With regard to the children, one does not afflict them by withholding food on Yom Kippur; however, one trains them one year before or two years before they reach majority, by means of a partial fast lasting several hours, so that they will be accustomed to fulfill mitzvot.

With regard to a pregnant woman who smelled food and was overcome by a craving to eat it, one feeds her until she recovers, as failure to do so could lead to a life-threatening situation. If a person is ill and requires food due to potential danger, one feeds him according to the advice of medical experts who determine that he indeed requires food. And if there are no experts there, one feeds him according to his own instructions, until he says that he has eaten enough and needs no more.

In the case of one who is seized with the life-threatening illness bulmos, causing him unbearable hunger pangs and impaired vision, one may feed him even impure foods on Yom Kippur or any other day until his eyes recover, as the return of his sight indicates that he is recovering. In the case of one whom a mad dog bit, one may not feed him from the lobe of the dog’s liver. This was thought to be a remedy for the bite, but the Rabbis deem it ineffective. And Rabbi Matya ben Ḥarash permits feeding it to him, as he deems it effective. And furthermore, Rabbi Matya ben Ḥarash said: With regard to one who suffers pain in his throat, one may place medicine inside his mouth on Shabbat, although administering a remedy is prohibited on Shabbat. This is because there is uncertainty whether or not it is a life-threatening situation for him, as it is difficult to ascertain the severity of internal pain. And a case of uncertainty concerning a life-threatening situation overrides Shabbat.

Similarly, with regard to one upon whom a rockslide fell, and there is uncertainty whether he is there under the debris or whether he is not there; and there is uncertainty whether he is still alive or whether he is dead; and there is uncertainty whether the person under the debris is a gentile or whether he is a Jew, one clears the pile from atop him. One may perform any action necessary to rescue him from beneath the debris. If they found him alive after beginning to clear the debris, they continue to clear the pile until they can extricate him. And if they found him dead, they should leave him, since one may not desecrate Shabbat to preserve the dignity of the dead.

A sin-offering, which atones for unwitting performance of transgressions punishable by karet, and a definite guilt-offering, which is brought for robbery and misuse of consecrated items, atone for those sins. Death and Yom Kippur atone for sins when accompanied by repentance. Repentance itself atones for minor transgressions, for both positive mitzvot and negative mitzvot. And repentance places punishment for severe transgressions in abeyance until Yom Kippur comes and completely atones for the transgression.