The revelation at Mount Sinai temporarily transforms the mountain into a sanctuary. Just as a physical temple contains both permitted and forbidden zones, a total separation is established between the Divine and human realms [שד״ל, קאסוטו]. This restriction emphasizes that God is elevated above nature, ensuring the boundaries between humanity and the Creator are never blurred [קאסוטו].
To enforce this separation, physical markers are placed on the ground so the Israelites know exactly how close they may approach [רשב״ם, רש״י, ביאור יש״ר]. Although these markers surround the mountain on all sides—not just the eastern slope where the Divine Presence is revealed [חזקוני]—the restriction is placed upon the people rather than the mountain itself. Since an inanimate mountain cannot receive commands, it is the humans who are required to halt at the mountain's edge, marking the beginning of the Israelite camp [הכתב והקבלה, אבן עזרא]. An alternative perspective suggests that restricting the people involves arranging them in specific places according to their status, serving as a preparation for the future organization of their camps and flags [העמק דבר, שפתי כהן].
The primary approach among commentators is that the boundary itself acts as a silent warning sign, constantly reminding the nation not to cross [רש״י, משכיל לדוד, דברי דוד]. From this, Moses deduces that if a silent, inanimate boundary serves as a warning, he must certainly warn the people with explicit words [גור אריה, מזרחי]. Another view notes that the Israelites actively warned one another to maintain the proper distance [חזקוני].
The restriction operates on two distinct levels. First, there is a strict prohibition against ascending the mountain, which forbids even entering its airspace without touching the ground, such as walking across a bridge [דברי דוד]. Second, there is a total ban on touching even the lowest edge of the mountain, not just the peak where God descends [רש״י, ברטנורא על התורה, אבן עזרא]. This rule applies even to someone standing safely outside the boundary who merely reaches a hand across the line to touch the mountain's base [שפתי חכמים].
The threat of the death penalty is introduced to prevent a situation where the Israelites, driven by intense spiritual enthusiasm, might tear down the boundary to witness the revelation. Such a breach would result in mass casualties, defiling the sacred space with bodies and turning the joy of the revelation into a mourning that would drive away the Divine Presence [ספורנו]. While the boundary was established immediately to train the nation to treat the site with reverence, the actual death penalty for touching the mountain only took effect on the third day, when God's presence finally descended [אור החיים]. The severity of this violation is absolute. An individual who touches the mountain and incurs the death penalty becomes forbidden to touch; no one may lay hands on him to carry out the execution, and he must instead be put to death from a distance [רא״ש].
Beyond the immediate physical instructions, this boundary carries a deep philosophical meaning. The physical barrier symbolizes the limits of human intellect. Just as staring directly into the blazing sun will cause blindness, attempting to investigate Divine matters that lie beyond human comprehension can cause severe spiritual harm or lead to an abandonment of faith. A person must humbly recognize the limits of their own mind and refrain from breaking through them [מלבי״ם].