יחזקאל, פרק ז׳, פסוק י״ז

The sheer terror of an approaching enemy creates a state of total physical and mental paralysis. This overwhelming danger effectively neutralizes the two most basic human survival instincts in a crisis: the drive to fight and the urge to run away [מלבי״ם]. The people experience a profound physical weakness, completely losing the strength and capability to hold their weapons and defend themselves against their attackers [רד״ק, מצודת דוד, מלבי״ם]. This severe loss of power in their hands eliminates any possibility of engaging in battle [מצודת ציון, ביאור שטיינזלץ].

At the same time, the ability to escape is entirely stripped away as their legs buckle under the weight of panic [מלבי״ם, ביאור שטיינזלץ]. The imagery of knees turning to water vividly captures this absolute terror, and there are a few ways to understand this severe physical reaction. It is viewed by some as heavy sweat pouring down the body as a result of intense fear [רש״י, מלבי״ם, מצודת דוד]. Others read it as a metaphor for a complete loss of stability, as though the knees have melted into liquid from panic, leaving the person entirely unable to stand [רד״ק, מצודת דוד]. Finally, it is also understood as a direct physiological reaction to sudden shock, where the paralyzing fear causes a complete loss of bodily control, resulting in urine running down the legs [ביאור שטיינזלץ].