Halakhah zu Keritot 2:7

He prohibited us from eating on the fast of Yom Kippur. But the Torah is not explicit about the prohibition of this act. Rather it mentions the punishment and makes one who eats liable for excision, such that we know he is prohibited from eating. And that is His saying, "For any person who will not be afflicted, etc." (Leviticus 23:29). And at the beginning of Keritot (Keritot 2a) when they listed those who are liable for excision, they listed among them, one who eats on Yom Kippur. And they explained there, that everything for which we are liable excision is a negative commandment - except for the Pesach-sacrifice and circumcision. Behold it has been confirmed that eating on Yom Kippur is a negative commandment. And therefore we are liable for excision for its volitional [transgression]; and a fixed sin-offering for its inadvertent [transgression] - as they explained at the beginning of Keritot, and as it is explained in Tractate Horayot (Commentary on the Mishnah on Keritot 2:3-4) - that this law is only mandated for a negative commandment, because of His saying about those that are liable for a fixed sin-offering, "one of the commandments of the Lord [concerning things] which should not be done." (Leviticus 4:13). And the language of the [Sifra] (Sifra, Emor, Chapter 14:4,9) is, "'For any person who will not be afflicted' - this is the punishment for the [non-] affliction. But we have not heard the prohibition about the [non-] affliction [on the day of Yom Kippur] itself! It is when it states the punishment for work. For let it not be stated, since it may be derived a fortiori, viz.: If [non-] affliction, [the ban against which] does not obtain on holidays and Shabbat, is [on Yom Kippur] punishable; then work [the ban against which] does obtain on holidays and Shabbat, how much more so should it be punishable! Why, then, is the punishment for work stated? To derive from it the prohibition against [non-] affliction: Just as the punishment for labor follows a prohibition, so [too] does the punishment for [non-] affliction follow a prohibition." Behold what we have said is explained. And the regulations of this commandment have already been explained in Tractate Yoma. (See Parashat Emor; Mishneh Torah, Rest on the Tenth of Tishrei 1.)