The arrival of the Israelites at the border of Moab triggers a profound psychological crisis and existential anxiety among the local inhabitants. Having just witnessed the complete destruction of the regional powers of Sihon and Og, the Moabites are terrified. Although the Israelites have not launched a direct attack, the mere presence of such a powerful nation on their border shatters their peace. This deep terror [רש״י, אבן עזרא] drives the panicked Moabites to gather together and seek refuge within their fortified cities [פענח רזא, הכתב והקבלה].
The Moabites are well aware that God commanded the Israelites not to wage war against them, yet their fear persists for several reasons. They worry that the Israelites might plunder their surrounding areas, consume their crops like an ox devouring grass, or force them into paying heavy taxes [רמב״ן, ספורנו, קה״ת]. Additionally, because the Israelites recently captured territories from Sihon that originally belonged to Moab, the Moabites suspect that their new neighbors might find a similar excuse to conquer the remainder of their land [חזקוני, נחל קדומים].
This anxiety is magnified by the sheer scale of the threat. The primary approach among commentators is that the Israelites possess an overwhelming population that has multiplied beyond the bounds of nature [רמב״ן, חתם סופר], coupled with an extraordinary military and spiritual strength that neutralizes any opposing force [רש״ר הירש, אדרת אליהו (ר' יוסף חיים)]. Alternatively, another perspective suggests that it is actually Moab's own size that makes their reaction so striking; despite being a large and significant nation themselves, they are still overcome by an immense dread of the Israelites [חתם סופר].
Eventually, this fear deepens into absolute despair. The Moabites feel a crushing distress that makes them sick of their own lives [רש״י, רשב״ם, ספורנו], sensing that their world is collapsing [אבן עזרא] and that their ultimate end has arrived [שפתי כהן]. Commentators note a fascinating progression in this panic, divided into two distinct stages. First, the Moabites are terrified of the common masses, or the mixed multitude traveling with the Israelites, fearing these groups might loot their land or attack independently without official orders [העמק דבר, חתם סופר]. Second, they experience a deeper dread stemming from the spiritual, moral, and religious greatness of the Israelites. Witnessing open miracles and recognizing that Israel's stature is built on an unbreakable, intrinsic holiness, the Moabites feel entirely inferior. They realize their physical might is meaningless against a nation guided by Divine providence [רש״ר הירש, מלבי״ם, אדרת אליהו (ר' יוסף חיים), הכתב והקבלה]. Ultimately, Moab understands that they are not merely facing a military opponent, but a Divine nation that is reshaping reality itself.