Affliction on Yom Kippur
The prohibitions of Yom Kippur are formulated in positive terms, e.g., “You shall afflict your souls” (Vayikra 16:31), rather than in negative terms, e.g., “You shall not eat.” For this reason, Rambam (Sefer HaMitzvot, Aseh 164) counts the prohibitions of Yom Kippur among the positive commandments: “He commanded us to fast on the tenth of Tishrei.” Rambam also records a negative commandment (Lo Taaseh 196): “He prohibited us to eat on the fast of Kippur,” but there is no explicit source for such a prohibition in the Torah. Rather, the prohibition against eating on Yom Kippur is inferred from the fact that one who eats on Yom Kippur is liable to the punishment of karet (excision), as the Mishna at the beginning of Karetot implies that only negative commandments can be subject to that punishment (with the exception of two specific positive commandments, circumcision and the Paschal offering).
In contrast to Rambam, Rabbi Saadia Gaon does not recognize a prohibition against eating on Yom Kippur, but only the positive commandment to afflict one’s soul. Rabbi Yeruham Fishel Perlow (in his notes to Rabbi Saadia Gaon’s Sefer HaMitzvot, Aseh 55) rejects Rambam’s proof from the Mishna in Karetot. He argues that it is possible that circumcision and the Paschal lamb are the only positive commandments mentioned there because only in those cases is karet imposed even though the transgression is committed by passively refraining from doing something that the Torah requires. The positive commandment banning eating on Yom Kippur may also be punishable by karet, but it is not mentioned in the Mishna because this transgression involves an actual action.
In light of the fact that the prohibition against eating on Yom Kippur is not explicitly mentioned in the Torah, it is possible to contemplate whether that prohibition is similar to other prohibitions against eating, or is merely a fulfillment of the positive commandment. For example, the Shaagat Arye (76) considers the possibility that even though eating in an unusual manner is not considered eating in other realms of the Torah, it could be that one who eats in an unusual manner on Yom Kippur is liable, since by doing so he avoided afflicting himself. The Binyan Tziyyon (34) even raises the possibility that one who already ate on Yom Kippur can no longer fulfill the obligation of affliction, and as such would not be liable for karet for any additional eating. Ultimately, though, he rejects this possibility, because he could not find a Rishon who accepts it.
How does one fulfill the obligation of “affliction”? All the Rishonim understand that it includes a prohibition against eating and drinking, for which the punishment of karet is imposed, but they disagree about whether the other afflictions, such as wearing leather shoes, are prohibited by Torah law or by rabbinic decree.
According to the Rosh, the other afflictions are forbidden only by rabbinic decree. He explains that this is why there are certain leniencies in these laws, such as that the king and queen are permitted to wash their faces. However, the Ran believes these prohibitions are also mandated by Torah law, as part of the commandment “you shall afflict your souls” or based on the word “sabbath.” He maintains that the Torah nevertheless delegated to the Sages the authority to determine which specific actions are forbidden and which are permitted, and explains that this accounts for the various leniencies.
According to Rambam (Sefer HaMitzvot, Aseh 164), all of the afflictions are required by Torah law: “It has come down to us by way of tradition that washing, anointing, wearing [leather] shoes, and sexual relations are forbidden [by Torah law], and that one is obligated to desist from all of these activities.” The Aharonim have suggested various explanations for the leniency regarding washing, according to the Rambam’s understanding that the prohibition is required by Torah law. For example, some say that Torah law only forbids a person to wash his entire body, and therefore washing one’s face is forbidden by rabbinic decree, and is therefore permitted in the case of a king and a queen. There is also room to consider whether the principle of “half the legal quantity” applies to washing. However, that requires a more lengthy analysis.
(Excerpted from Rav Binyamin Tabory, The Weekly Mitzva [Maggid, 2015].)