Midrasch zu Wajikra 16:29

1) (Vayikra 16:29) ("And it shall be to you an eternal statute: In the seventh month, on the tenth day of the month, you shall afflict your souls. And all work you shall not do, the citizen and the stranger that sojourns in your midst.") "And it shall be to you" (for atonement): and not to idolators. "an eternal statute": for the eternal house (i.e., the Temple, to exclude sacrificial mounds, where those offerings are not sacrificed.) "in the seventh month": I might think all of it; it is, therefore, written "on the tenth day of the month." "you shall afflict your souls": I might think that one should sit in the sun or in the cold in order to afflict himself; it is, therefore, written, (following:) "And all work you shall not do." I have forbidden work to you in a different context (Shabbath), and I have forbidden (non-) affliction (by eating) in a different context. Just as the work that I forbade you in a different context is work which is liable to kareth (cutting off), so, the (non-) affliction that I forbade you in a different context is such that is liable to kareth.

2) And these are (the eating of) nothar (portions of sacrifices "left over" beyond the permitted eating time) and (the eating of) piggul (sacrifices invalidated by improper intent of the officiating Cohein). Whence is (the eating of) tevel (untithed produce) to be derived? From "shall you afflict your souls," this ("your souls") serving as an inclusion.

3) I would then include tevel, which is subject to the death penalty; but I would not include neveilah (carcass), which is not subject to the death penalty; it is, therefore, written (in several places) "you shall afflict your souls" to include (all these). I would include neveilah, which is subject to a negative commandment, but I would not include chullin (mundane food), which is not subject to a negative commandment; it is, therefore, written (in several places) "you shall afflict your souls" (to include (all these). I would include chullin, which is not subject to a positive commandment, but I would not include terumah and second-tithe, which are (in some instances) subject to a positive commandment (e.g., in respect to Cohanim). It is, therefore, written "you shall afflict your souls," for inclusion. I would include terumah and second-tithe, which are not subject to "And you shall not leave over" (Vayikra 22:30); but I would not include consecrated food, which is subject to it; it is, therefore, written "you shall afflict your souls," for inclusion. Variantly: "You shall afflict your souls" — affliction which affects (the preservation of) your souls. Which is that? (Abstention from) eating and drinking.