The Mekhilta draws attention to a strange detail about the drowning of the Egyptian army at the Red Sea. When God cast "a horse and its rider" into the sea, something happened that defied the normal laws of nature.
Under ordinary circumstances, when someone throws two objects into the sea, they immediately separate. The current pulls them apart, the waves scatter them in different directions. Anyone who has tossed two things into water knows this — they drift away from each other almost instantly.
But at the Red Sea, something different occurred. The horse was bound to its rider, and the rider to the horse, and they rose and descended together through the depths without ever separating. The Egyptian cavalryman and his mount went into the water as a single unit and remained fused together as they plunged to the bottom. No current could part them. No wave could pull them apart.
This detail transforms the drowning from a natural disaster into a deliberate act of divine precision. The sea did not simply swallow the army in chaos. God bound each rider to his horse so that the very partnership that made them powerful on dry land — the cavalry bond between warrior and warhorse — became an inescapable trap in the water. The rider could not abandon his horse to swim. The horse could not throw its rider to surface for air.
The Mekhilta's observation is characteristically precise: "A horse and its rider — together He cast into the sea." Together on land in arrogance. Together in the depths in judgment.