תהלים, פרק ק״ה, פסוק ל״ו

The final and most devastating plague brought upon Egypt was the death of the firstborn. God directed this fatal strike exclusively at the Egyptians, intentionally sparing the firstborn of the Israelites [אבן עזרא]. To emphasize the sheer magnitude of this event, poetic repetition is used to reinforce the message of widespread destruction [רד״ק, מצודת דוד].

The plague struck the land of Egypt directly [ביאור שטיינזלץ], but the devastation within its borders was not limited to the native population. It also claimed the lives of firstborns from other nations who happened to be staying in Egypt at the time [אלשיך]. While the primary approach among commentators is to read the poetic structure as a repetition for emphasis, others identify a specific geographic distinction. In this view, the plague reached far beyond the borders of Egypt, striking down Egyptian firstborns wherever they were in the world, even if they lived far from their homeland [מלבי״ם].

The concept of a firstborn is deeply connected to a parent's initial strength, representing the very first sons brought into the world [מצודת ציון, מאירי, אבן עזרא, מצודת דוד]. This connection reveals a severe expansion of how a firstborn was defined during the plague. The strike was not restricted merely to the firstborn of a mother. Instead, it applied to any child who was the firstborn to his father. As a result, in situations where a single woman had children with multiple men, every single son who was the firstborn to his respective father perished in the plague [אלשיך].