Yoma, Chapter 8, Mishnah 3. Our Mishnah continues the discussion of the measures of eating and drinking on Yom Kippur that were explained in the previous Mishnah, and it deals with two matters: the number of sin offerings incurred by one who transgressed unintentionally, and the law of one who consumes foods and liquids that are not fit for consumption.
"Achal v'shasah b'helem echad - eino chayav ela chatas achas":
"Achal v'shasah b'helem echad" - a person who ate the required measure and drank the required measure, according to the measures explained in the previous Mishnah, and did so within a single lapse of awareness: he forgot that the day was Yom Kippur, or he was unaware that eating and drinking are forbidden on it. This lapse is what defines his act as unintentional and obligates him in a sin offering. In such a case the Mishnah rules: "eino chayav ela chatas achas" - he is liable to only one sin offering, and not two separate sin offerings, even though two different acts are involved.
The reason for this: as we mentioned in the previous Mishnah, the measures of eating and drinking do not combine with one another, and nevertheless both are included in a single prohibition - the prohibition of afflicting oneself. Therefore, one who performed both acts, each in its own measure, but within a single lapse and a single forgetting, is liable to only one sin offering.
"Achal v'asah melachah - chayav shtei chataos":
By contrast, one who ate and also performed work that is forbidden on Yom Kippur is liable to two sin offerings - two separate offerings, because his acts stem from two entirely different prohibitions in the Torah:
The prohibition of afflicting oneself - the obligation to afflict oneself on Yom Kippur, from which the prohibition of eating and drinking is derived.
The prohibition of work - "v'chol melachah lo sa'asu" - and you shall do no manner of work.
Since two separate prohibitions are involved, the sin offerings are two as well.
"Achal ochlin she'einan re'uyin la'achilah":
The Mishnah goes on to list cases in which the act is not considered eating or drinking in the normal manner:
"Achal ochlin she'einan re'uyin la'achilah" - he ate food that is not fit for eating, such as bitter herbs or anything that people do not normally eat.
"V'shasah mashkin she'einan re'uyin lish'tiyah" - he drank a liquid that is not fit for normal drinking, such as undiluted vinegar.
"Tzir" - the brine of salted fish, the liquid that comes out of fish that were salted.
"Muryas" - the fat or sauce that comes out of pickled fish.
In all of these the Mishnah rules: "patur" - he is exempt from kareis, since these are not items that are eaten and drunk in the normal manner. True, people do use tzir and muryas in another way, dipping in them and using them in small quantity, but it is not normal to drink them undiluted, and therefore there is no liability.
Nevertheless, the act is forbidden by rabbinic law, and one who transgresses it receives, in practice, makkas mardus - rabbinic lashes.
In summary: in this Mishnah we learned that eating and drinking within a single lapse of awareness obligate only one sin offering, since both stem from the single prohibition of afflicting oneself, even though their measures do not combine; whereas eating and performing work obligate two sin offerings, because they stem from two separate prohibitions. We also learned that one who eats foods that are not fit for eating or drinks liquids that are not fit for drinking, including tzir and muryas, is exempt from liability - but the act is forbidden by rabbinic law and he receives makkas mardus.