שמות, פרק ז׳, פסוק כ״א

The plague of blood struck at the very heart of Egypt, transforming the nation's primary source of life and abundance into a site of death, stench, and starvation. This devastation served as a direct, proportional punishment for Pharaoh's cruel decrees. Because he spilled the innocent blood of Israelite children into the Nile, its waters were turned to blood. Because he sought to suppress the Israelites, who were multiplying rapidly like fish, the fish of the river were condemned to die. Finally, because Pharaoh was disgusted by the very existence of the Israelites, his beloved river was rendered utterly foul and repulsive [ביאור יש״ר].

The unfolding of the plague followed a precise sequence. Initially, Moses struck the Nile, and the fish within it died immediately [רשב״ם]. This devastation did not just affect a few isolated creatures, but rather a massive multitude of fish and aquatic life [הכתב והקבלה]. As their bodies rotted, worms bred within the decay, creating an unbearable stench [קיצור בעל הטורים]. Only after this initial strike did Aaron stretch out his staff, causing the blood to spread outward to all the other water sources across the land of Egypt [קאסוטו, העמק דבר]. Stripped of their surface water, the Egyptians were desperately forced to dig pits in search of anything to drink [צאינה וראינה].

The fatal nature of the plague served a crucial purpose: it proved to the Egyptians that this was an absolute act of God, rather than a mere demonic trick or magical illusion. While sorcery can conjure visual deceptions, it cannot extinguish life. The blood in the Nile, however, was entirely real and lethal to the fish. Further proving its divine origin, the blood retained its form no matter where it was transferred, even when brought into bathhouses. This stood in stark contrast to magical illusions, which dissipate the moment they are moved or placed upon the ground [אור החיים].

A profound division existed between the Egyptian and Israelite experiences during the plague. If an Egyptian and an Israelite drank from the exact same cup, the Egyptian would swallow blood while the Israelite drank pure water. Consequently, the Israelites acquired immense wealth by selling drinkable water to their desperate neighbors [הדר זקנים]. This raises a question regarding religious law, which generally forbids a person from deriving financial profit from a miracle. How, then, could the Israelites sell this water?

One explanation suggests that the physical reality of the Nile never actually changed; it remained regular water. The miracle only occurred subjectively within the hands and mouth of the Egyptian attempting to drink it. Because the miracle happened to the Egyptians and not the Israelites, the Israelites were permitted to profit. This perspective also explains why the death of the fish was a necessary detail to record. If the entire river had physically turned to blood, the death of the fish would be an obvious, natural consequence. However, since the river fundamentally remained water, the death of the fish was a separate, distinct miracle [פרדס יוסף]. Another approach resolves the issue by suggesting that the water sold to the Egyptians did not come from the Nile at all, but rather from separate Israelite water sources that had not been affected by the plague's initial spread [העמק דבר].