Yom Kippur represents the absolute peak of withdrawing from human activity, merging a complete halt of labor with a total detachment from physical needs. Unlike other holidays, this day requires a person to stop not only their external work but also their basic physical routine. The concept of rest on this day is absolute, surpassing any ordinary Sabbath, and the intensity of the command is heavily emphasized [אבן עזרא, ביאור שטיינזלץ, פירושי רד צ הופמן] to magnify the very idea of rest [מלבי״ם, אילת השחר].
The primary approach among commentators is that this profound rest operates on two distinct levels. The first level involves the standard cessation of weekday labor. The second, elevated level adds a strict avoidance of bodily needs and pleasures, such as eating and drinking. Furthermore, this higher degree of rest expands the restrictions to include actions that are not typically considered full labor, enforcing the obligation to practice all five forms of physical affliction observed on this day [רש ר הירש, אדרת אליהו, צפנת פענח, ביאור יש״ר].
This specific combination of rest and physical affliction is entirely unique to Yom Kippur and does not apply to a standard Sabbath, where fasting is actually forbidden [מלבי״ם, אדרת אליהו]. Yom Kippur holds a completely independent status. If it happens to fall on a regular Sabbath and a person performs labor, they carry a double responsibility for violating both days simultaneously [תורה תמימה, מלבי״ם]. Moreover, while a regular Sabbath is dedicated to God in order to declare Him as King, Yom Kippur is dedicated entirely to the Israelites for the sake of their atonement. By suspending their physical existence, people express their complete helplessness and absolute dependence on God [רש ר הירש, חזקוני, פרדס יוסף].
The requirement to afflict oneself demands an active, intentional withdrawal from bodily needs. This stands in sharp contrast to ordinary fast days, where people might wrongly continue their daily material business because they fail to grasp the true essence of the day [ספורנו]. Furthermore, because the surrounding laws detail the High Priest's service in the Holy of Holies, one might mistakenly assume that the holiness and restrictions of Yom Kippur depend entirely on the existence of the Temple. Therefore, it is made clear that the obligation to rest and fast is an eternal, independent law. It applies in every generation, even in the absence of a Temple and a High Priest [ספורנו, רלב״ג, ביאור יש״ר, ביאור שטיינזלץ, פירושי רד צ הופמן].
On a deeper level, the concept of this eternal law is closely tied to the idea of food and daily rations. Although fasting appears to be a denial of physical nourishment, the very merit of fulfilling this commandment provides a person with eternal spiritual food, granting merits that endure for all generations and into the World to Come [חתם סופר].