שמות, פרק ז׳, פסוק י״ח

The first plague struck at the very heart of Egypt by transforming its life-giving river into a scene of total ecological collapse. The goal was not merely to change the color of the water, but to completely strip the Egyptians of their ability to use their primary water source. The destruction included all creatures living in the water, from the smallest to the largest [אבן עזרא, תורה תמימה]. The death of these creatures served a crucial purpose. It proved that the plague was an actual, physical transformation of the water into real blood, rather than a mere optical illusion produced by the magicians [ספורנו, תולדות יצחק].

From a natural standpoint, the water creatures perished because they rely on cold, moist water to survive, whereas blood is inherently warm [מלבי״ם, שטיינזלץ]. However, there is also a moral and providential reason for their destruction. The fish were punished alongside the Egyptian people because they had fed on the bodies of the Israelite babies who were previously thrown into the river [תולדות יצחק].

This mass death caused the river to emit a terrible stench, which played a central role in the plague. Technically, blood is a liquid that desperate people might drink to survive extreme thirst. To prevent the Egyptians from drinking the blood even as a last resort, the rotting fish made the river so foul that it became entirely undrinkable [הכתב והקבלה, ביאור יש״ר, דעת זקנים]. While some suggest that the water only turned to blood briefly and the ongoing plague was simply the stench of the dead fish [פענח רזא, בכור שור מובא בפני דוד], the primary approach among commentators rejects this idea. The consensus maintains that the river remained actual blood throughout the entire duration of the plague [פני דוד].

Faced with this severe crisis, the Egyptians experienced profound weariness, frustration, and an absolute inability to drink [אבן עזרא, רשב״ם, רש ר הירש]. Commentators offer different explanations for the source of this exhaustion. One approach explains that the Egyptians tired themselves out in desperate, futile attempts to purify and perfume the foul-smelling blood to make it fit for consumption [רש״י, מזרחי, גור אריה, ביאור יש״ר]. Another perspective suggests that their weariness came from the intense physical labor of digging new wells all around the river in a frantic search for alternative water sources [ספורנו].