Halakhah su Levitico 23:29

The Torah (Vayikra 23:29) teaches that one who eats on Yom Kippur is punished with kareit (spiritual excision).¹Rashi (Vayikra 17:9 s.v. V’nichrat and 20:20 s.v. Aririm) mentions that kareit can entail dying childless, burying one’s children, or dying prematurely. The Gemara (Mo’eid Katan 28a) defines “prematurely” as before age fifty. This punishment takes effect, according to the Mishnah (Yoma 8:2), only if he eats or drinks the shiur (requisite amount), which, for Yom Kippur, is a volume of food equivalent to the size of a large date (kakotevet hagasah) or a quantity of liquid that could fill one’s cheek (melo lugmav).

And [it] is practiced in every place and at all times by males and females. And one who transgresses it and ate like the measure of a ketovet on Yom Kippur has violated a positive commandment, and has [also] transgressed a negative commandment that has [a liability of] excision for it; as is is stated (Leviticus 23:29), "For any soul which is not afflicted on that very day shall be excised." [If] he ate or drink like this measure inadvertently, he is liable for a fixed sin-offering.

To not eat and drink on Yom Kippur: To not eat and drink on Yom Kippur, as is is stated (Leviticus 23:29), "For any soul which is not afflicted on that very day shall be excised." And I have written all of the content of this commandment above in this Order in Commandment 313 (Sefer HaChinukh 313). See there, 'for it is close.'