Heading into the climactic moment of the Exodus from Egypt and immediately prior to the Plague of the Firstborn, we encounter a fairly strange command:

Speak to the entire community of Israel, saying, "On the tenth of this month, let each one take a lamb for each parental home, a lamb for each household… And they shall take [some] of the blood and put it on the two doorposts and on the lintel, on the houses in which they will eat it… I will pass through the land of Egypt on this night, and I will smite every firstborn in the land of Egypt, both man and beast, and upon all the gods of Egypt will I wreak judgments I, the Lord.

And the blood will be for you for a sign upon the houses where you will be, and I will see the blood and skip over you, and there will be no plague to destroy [you] when I smite the [people of the] land of Egypt.1

Within the famous order to sacrifice a lamb on the eve of the Exodus lies the instruction to take its blood and mark it upon the doorpost. While the text provides some explanation, many questions remain. What exactly was this “sign”? Does G‑d require a physical marker to identify Jewish homes? And why blood?

1. It Was a Marker for the Destroying Angel

Ibn Ezra explains that the blood was a sign to ensure the angel of destruction would not enter the Jewish homes.

He says that the blood was placed on the entrance to the individual houses within each courtyard. The courtyard gates were kept closed so that the Egyptians—who saw sheep as deities—would not see the blood and become enraged that the Jews had sacrificed their gods.2 For the same reason, to avoid drawing attention, the slaughtering was done after nightfall.3

2. The Blood Showed the Boldness of the Jews

Others suggest the exact opposite: the blood was placed on the outside specifically to provoke the Egyptians.4 Rabbeinu Bachye elaborates, explaining that this is also why the lamb was required to be roasted—to ensure its aroma would spread, making their actions widely known.

This open display of allegiance to G‑d, even amidst the pervasive idolatry of Egypt, was what made them worthy of redemption. By boldly rejecting the evil influences around them, they demonstrated their steadfast commitment to G‑d and their spiritual readiness for liberation.5

3. It Signifies Life

Rabbeinu Bachye cites a verse in Leviticus which states that “blood is the soul.”6 The blood, therefore, symbolized both death for the Egyptians—referring to the Plague of the Firstborn—and life for the Israelites. It served as a sign of protection, indicating that the “destroyer”7 had no permission to harm the Jewish people. 8

4. The “Destroyers” Came Along for the Ride

He then addresses an obvious question.9 If the blood protected the Jews from the “destroyer,” does this imply that G‑d did not personally carry out the Plague of the Firstborn, instead delegating it to an angel or destructive force? This seems to contradict the plain reading of the verses and many comments of the sages.10

Rabbeinu Bachye clarifies that it was indeed G‑d Himself who struck the Egyptian firstborns. However, moments of destruction inherently create opportunities for other destructive forces to act. The “destroyer” mentioned in the verse was not the primary executor of the plague, but a destructive force drawn to the chaos. The blood served to protect the Jewish homes from these secondary forces, ensuring they remained untouched by the wider destruction.11

5. It Symbolized the Blood Placed on the Altar

The blood of Temple sacrifices was typically sprinkled, smeared, or poured onto the altar. For the Paschal Sacrifice, the blood was collected in a designated cup and poured at the base of the altar. The Talmud notes that in Egypt, the lintel and doorposts served as a symbolic stand-in for the altar of the Tabernacle and, later, the Temple.12

6. It Was the Proto-Mezuzah

The Mechilta compares the protection of the blood placed on the doorposts to the protection offered by affixing a mezuzah to one's doorpost.

Is this not a fortiori (kal vachomer) argument? If about the blood of the Paschal Sacrifice in Egypt, which was lighter in weight—it was temporary, applicable only at that moment, not observed by day and night, and not commanded for future generations—it was said, “And He will not allow the destroyer [to strike],”13 then how much more so the mezuzah, which is more stringent! It contains ten unique Divine names, is observed by day and night, and is a commandment for all generations. All the more so that “He will not allow the destroyer” to enter!14

7. It Showed G‑d’s Essential Love

The Rebbe explains that the Plague of the Firstborn stemmed from a level of G‑dliness beyond the limits of the natural order, reflecting G‑d’s essence which transcends judgment and logic. From this perspective, the argument that the Jews were unworthy of being redeemed, due to their low spiritual level, has no import. This revelation highlighted G‑d’s boundless love for the Jewish people, a love that defies rational accusations or comparisons.

To channel this transcendent love into the physical realm, however, the Jews needed to take action. They marked their doorposts with the blood of the Pesach offering (which also symbolized the blood of circumcision), acts that demonstrated a supra-rational commitment to G‑d. These signs symbolized their active participation in drawing down G‑d’s infinite love, transforming it into tangible protection and paving the way for their redemption.15

8. The Blood Transformed the Home Into a Miniature Temple

These events occurred at the time of the birth of the Jewish nation. Therefore, explains the Rebbe, it needed to emphasize the ultimate purpose of the Divine service of the Jewish people: to fulfill the commandment “I will dwell among them”16—specifically within each and every Jew—to the extent that their home becomes a place for the Divine Presence to rest.

This is why each household was required to slaughter their own lamb within their home and place the blood on the doorframe. By performing the mitzvot associated with offering a sacrifice in their own space, they transformed their homes into a microcosm of the Temple.

In future generations, however, the Passover Sacrifice could only be brought in the Tabernacle or Temple, where the Divine Presence was openly revealed. Offering the sacrifice outside these sanctified spaces is prohibited. This is because the Tabernacle or Temple embodied the fulfillment of “I will dwell among them,” channeling the Divine Presence into the collective service of the Jewish people. Before the Giving of the Torah and the building of the Tabernacle, however, the emphasis was on actualizing “I will dwell among the” within each individual, transforming their homes into sanctuaries for G‑d’s presence.17