The climax of the plagues brought a devastating judgment upon Egypt, yet the Israelites were offered a path to salvation. This rescue, however, was not automatic; it required an active display of faith, a complete break from their enslaved past, and profound self-sacrifice.
God instructed the Israelites to place blood on their homes, raising a natural question: why would an all-knowing God require a physical marker? The primary approach among commentators is that the sign was entirely for the Israelites themselves, not for God. By taking a lamb—a sacred animal to the Egyptians—slaughtering it, and applying its blood, the Israelites demonstrated a total rejection of Egyptian idolatry. This bold act required them to act without fear of their neighbors' retaliation, serving as a powerful testament of their repentance and absolute trust in God [הכתב והקבלה, ספורנו, רבנו בחיי, אלשיך, רלב״ג].
The exact placement of this blood is a matter of fascinating debate. The primary approach among commentators suggests the blood was applied to the inside of the doorframes. In this way, it served as a private, internal reminder for the Israelites, unseen by the outside world [רש״י, תורה תמימה]. Conversely, others argue that the blood was deliberately placed on the outside, in full view of the Egyptians. This public display was meant to project utter fearlessness and to visibly shatter the terror of Egyptian idolatry [הכתב והקבלה].
When God looked upon the blood, it was not an act of physical sight, as everything is already revealed to Him. Rather, this seeing was metaphorical. It meant that God focused His attention on the Israelites' pure intentions and the merit they gained by fulfilling His Commandment [רש״י, מלבי״ם, חזקוני]. A deeper perspective suggests that God was not only looking at the blood of the Passover offering but was simultaneously seeing the blood of the Binding of Isaac. It was this ancient ancestral merit that stood by the Israelites, shielding them from the unfolding disaster [רבנו בחיי, מלבי״ם].
The divine act of passing over the homes carries two distinct meanings. One approach interprets the concept as an expression of compassion, mercy, and protection, emphasizing that God would spare and rescue the Israelites without attributing physical movement to Him [רש״י, הכתב והקבלה, נתינה לגר]. A more literal interpretation suggests actual skipping or leaping. Because the homes of the Israelites and Egyptians were thoroughly mixed together in the same neighborhoods, God literally leaped from one Egyptian house to the next, skipping over the Israelite homes in between [רש״י, בכור שור, חזקוני, ברכת אשר].
The night of the plague unleashed chaotic forces of destruction. Typically, when a destructive force is set loose, it does not distinguish between the righteous and the wicked. This danger was compounded by the natural spread of disease that would arise from the sheer number of Egyptian casualties. Therefore, a special divine guarantee was necessary to ensure that the destructive force would be restrained and denied permission to harm Israel [ספורנו, אור החיים, בית הלוי, שד״ל, קאסוטו]. This protection was so absolute that even an Israelite who was naturally destined to die of old age or illness that very night was kept alive. This prevented the Egyptians from ever claiming that the plague had struck the Israelites as well [נחלת יעקב].
Yet, this extraordinary immunity was strictly exclusive to the Israelites. If an Egyptian attempted to escape the plague by hiding inside a Jewish home, the protective power of the Commandment did not cover him, and the destroyer struck him down right there. On the other hand, if an Israelite happened to be inside an Egyptian home that night, personal divine providence shielded him from sharing the Egyptians' fate [רש״י, מזרחי, אור החיים]. Ultimately, while a time of divine anger brings swift punishment that threatens to consume everyone in its path, God's mercy overpowered the chaos, granting the Israelites impenetrable immunity amidst the devastation [העמק דבר].