(5) I have tried to find a reason why the dying of the firstborn was a necessary prerequisite for the Exodus, as well as why even non-Egyptian firstborn (compare 12,29) had to die if they happened to be in Egypt on that fateful night. The reason is connected to G'd having described Israel as "My firstborn son" (4,22). We have a tradition (Zohar 2, page 263) that whenever G'd created some phenomenon which is clearly recognisable as something good, He also created its counterpart, i.e. something potentially evil at the same time. Every sacred phenomenon in our world is matched by a parallel phenomenon under the control of Satan, or what is known in Kabbalistic parlance "the forces of the קליפה." The latter make every effort to gain dominance over the former. We must therefore understand the forces of the קליפה which represented their firstborn as exerting every effort to frustrate the emigration of the Jewish people from Egypt. These efforts did not cease until G'd had "killed" the firstborn of the powers of the קליפה which opposed His will. What G'd had to do was to eliminate the concept of the firstborn being special, otherwise the relief as a result of the death of the Egyptian firstborn would have been only temporary. When the Torah (12,29) stresses that: "the firstborn of the captive, the firstborn of the maidservant and the firstborn of the animals died," this is in contrast to the firstborn of the Israelites who were subsequently sanctified (Numbers 8,17). The reason this sanctification of the Jewish firstborn became necessary is that G'd had done away with the concept of the firstborn being somebody special at the time He eliminated the firstborn on the night of the 15th of Nissan. Had this not been the case we would not understand why the firstborn of the animals had to die also. In Numbers 8,17 G'd declared that henceforth the firstborn of the Jews would be sacred to Him, i.e. there should no longer be a firstborn associated with the powers of the קליפה. If we find that the Egyptians still engaged in hot pursuit of the Israelites even after the death of the firstborn, this was because they had not yet realised that their former power had vanished. As a result, not a single one of them survived the debacle at the Sea of Reeds.
The side of holiness is nothing but the indwelling and extension of G‑d’s holiness. Now, G‑d dwells only on that which is surrendered to Him, whether [the surrender is an] actual [one] (and visible even in that surrendered being’s external aspects) as is the case with the supernal angels whose entire being is constantly and openly surrendered to G‑d or whether [it is a] potential [surrender], as in the case of every Jew here below in this physical world,who has the capacity for surrendering himself completely before G‑d, through martyrdom for the sanctification of G‑d’s Name.
That is why our Sages have said that “if even one individual sits and engages in Torah study, the Divine Presence rests upon him.”Also, “On each gathering of ten Jews the Divine Presence rests” always; together, ten Jews form a “congregation of Israel,” which is a fit abode for the Divine Presence.
Anything, however, that does not surrender itself to G‑d, but [considers itself as if it] is a thing separate unto itself, does not receive its life from the holiness of G‑d —
But where else would it receive its vitality? G‑dliness and holiness is the source of vitality for every existing being, as it is written, “You give life to them all” .
[The Alter Rebbe goes on to qualify his previous remark, stating that those beings who do not surrender themselves to G‑d receive their vitality only from a superficial, external level of G‑dliness; and from this level, too, only when it descends degree by degree through numerous “contractions” of the life-force. To return to the Alter Rebbe’s words:] The self-styled separate being does not receive its vitality from the pnimiyut,the inner aspect of holiness, from its every essence and core, but from its achorayim, its “hind-part”, so to speak.This limited form of life-force reaches the kelipot by descending degree by degree through myriads of levels, in the chain-like descent of the worlds, in the manner of cause and effect.
The vitality descends also through many tzimtzumim, or contractions — and this process diminishes the vitality to the point where it is incomparably lower than in its original state.
So greatly diminished does the light and life-force become, diminution after diminution, until it is able to become contracted and clothed in a manner of exile, meaning that instead of being surrendered to the Divine life-force, the object in which the vitality is clothed masters it; as, for example, a captive in exile is mastered by his own captor
The vitality is thus in a state of exile within that object which is (i.e., which considers itself) separate from holiness, giving it vitality and existence, causing that object to pass from non-existence to existence, so that is does not return to its original state of non-existence, as it was before it was created by the vitality clothed in it.
In brief: All that is not surrendered to G‑d, but considers itself separate from Him, receives its vitality from the achorayim of G‑dliness by way of numerous descents and various contraction. The Divine life-force is concealed within it in a state of exile; thus it belongs to the realm of kelipah. It is now clear why any thought, word or action not directed toward [serving] G‑d — hence, not surrendered to G‑dliness — is a garment of the animal soul that derives from kelipah,even if that thought, word or deed is not actually evil.
Rabbi Samson Raphael Hirsch on Exodus 11:5
This was the moment announced right at the beginning in Exodus 4:22-3, (“Then you shall say to Pharaoh, ‘Thus says the LORD: Israel is My first-born son. I have said to you, “Let My son go, that he may worship Me,” yet you refuse to let him go. Now I will slay your first-born son.’”), not out of hatred of your son, but to effect the salvation of My son. In the death of your son, you will learn to estimate My feelings at the mishandling of My son.
Deuteronomy 23,4. “No Ammonite or Moabite shall be admitted to the congregation of the Lord……because they did not meet you with food and water on your journey after you left Egypt.”
We know that G’d has described the Jewish people to Pharaoh as “My first born son”. (Exodus 4,22) What this really means is that the Jewish people are the conduit through which G’d channels His largesse to the world. Ammon and Moav denied the principle that the major objective of channeling largesse to mankind was for the glory of Israel, who would be perceived as the most important single link in that chain, indirectly benefiting all of mankind. By describing the Ammonites and the Moabites as not offering “bread and water” to the Jewish people, the Torah hints that they did not recognize the existence of the Jewish people as something beneficial for all of mankind.
וְאָמַרְתָּ֖ אֶל־פַּרְעֹ֑ה כֹּ֚ה אָמַ֣ר יי בְּנִ֥י בְכֹרִ֖י יִשְׂרָאֵֽל׃
Then you shall say to Pharaoh, ‘Thus says the L-RD: Israel is My first-born son.