What is the significance of midnight?
Rashbam: While Yisrael were eating their Korban Pesach.
Yevamos 72a: It teaches us that midnight (the moment the Ge'ulah came into effect), is a time of goodwill - and that consequently, the north wind, which did not blow throughout the forty years in the desert, 1 did blow every night at midnight.
See Torah Temimah, note 212, who elaborates at length
What are the ramifications of the letter Vav (the conjunctive and) in the word, "Va'Shem [Hikah Kol Bechor]"?
Rashi (citing the Yerushalmi Berachos, 9:5): Wherever one finds the word 1 "Va'Shem," it means Hashem together with His Beis-Din. 2
Seforno: With reference to the previous Parshah - Yisrael busied themselves with the Mitzvah of Korban Pesach; "and" Hashem at the very same time smote the Egyptians' firstborn. 3
Rashi: Bearing in mind the fact that the letter 'Vav' is intrinsically inclusive.
Rosh: This is why Iyov said, "Hashem Nasan, Va'Shem Lakach" (Iyov 1:21) - When Hashem gives free gifts to His creations, He does not consult with His entourage; but when He takes or afflicts, He consults with His Beis Din.
See Rashbam, who makes this comment on the words "ba'Chatzi ha'Laylah."
Why does the Pasuk insert the word "Kol Bechor"?
Rashi: To include the firstborn of other nations who happened to be in Egypt. 1
Gur Aryeh: Seemingly, Rashi made this same comment to 12:12 above (see 12:12:2.1); why does he repeat it here? Refer to 12:29:2.4:1.
Why does the Torah need to mention "mi'Bechor Pharaoh"?
Rashi: To hint at the fact that Pharaoh was himself a Bechor, and that Hashem spared him only in order to show him His strength at the Yam-Suf. 1
Rashi: As intimated above in 9:16.
What does the Torah mean when it writes, "from the firstborn of Pharaoh, who sits on his throne"?
Rashbam and Targum Yonasan: It means the crown prince, who would have succeeded Pharaoh had he not died in the plague of Makas Bechoros.
Why were the firstborn of the captives included?
Here, the Torah writes that Hashem struck the firstborns at midnight. But in Bamidbar 3:13 and Bamidbar 8:17, it writes "b'Yom Hakosi Kol Bechor"!
Riva (citing Rashi): R. Yochanan said, Hashem struck them at midnight, and they quivered the entire night until [they died] on the following morning. 1
Riva: It was midnight for the Bechoros, but day for Hashem. 2
Maharal: As for why Makas Bechoros took place at night, whereas the Geulah was by day, refer to 12:12:2 and its note.
QUESTIONS ON RASHI
Rashi writes: "'[Hashem] smote every firstborn [in the land of Egypt]' - Even those of other nations, who were [presently] in Egypt." How is this derived?
Gur Aryeh: Had the verse meant only Egyptian firstborns, it would have said only, 'Hashem smote all the firstborn of Egypt' -- leaving out the phrase "in the land of." 1
Rashi seemingly made the same derivation in verse 12:12 above. But see 12:29:2.4:1.
Rashi writes: "[Hashem] smote every firstborn [in the land of Egypt]' - even those of other nations...." But we find that Moshe used this same expression, when he warned Pharaoh about Makas Bechoros (in verse 11:5); and Rashi does not interpret this way in that context?
Gur Aryeh #1: There was no reason to warn Pharaoh of the impending death of the foreign firstborn in his land. Pharaoh couldn't care less. 1 (Nevertheless, it ultimately was a component of the Makah.)
Gur Aryeh #2: Perhaps in the context of verse 11:5, the phrase comes to include the firstborn of the captives (which are not mentioned there explicitly).
Gur Aryeh: This would also answer why Pharaoh was not warned about the firstborn of the captives - for he would not care (see 11:5:2.1). Moshe nevertheless did allude to the foreign firstborn in his warning (albeit not mentioning it explicitly), so that the Egyptians would not later accuse Moshe of not knowing the details of the Makah.
Rashi writes: "[Hashem] smote every firstborn' - even those of other nations...." But perhaps only the Egyptian firstborns (presently in Egypt) died? Our verse would then exclude any Egyptian firstborn who was not presently "in the land of Egypt," but rather abroad. (The verse that Rashi to 12:12 cited (Tehilim 136:9), as proof that even the Egyptians overseas were hit, could be re-interpreted that same way.)
Gur Aryeh: [The title of this Rashi is precise.] Rashi's derivation is not from the phrase "in the land of Egypt," 1 but rather, a Ribui (inclusion) from the word "Kol" - i.e. every firstborn, even the foreign ones. 2
Gur Aryeh: Had that been the case, we indeed could have said that both conditions were necessary - i.e., that only the Egyptian firstborn presently in Egypt were hit.
Gur Aryeh: And once we include even foreign firstborn, the verse in Tehilim must also include those Egyptian firstborn presently overseas.
Rashi writes: "'[Hashem] smote every firstborn' - ... Even those [firstborn] of other nations, who were [presently] in Egypt." But Rashi made this same derivation in 12:12; why need it be repeated?
Gur Aryeh: Looking closely, the derivations are not the same! In our verse, Rashi comments on the words "every firstborn;" whereas in 12:12, he comments on the phrase "... in the land of Egypt." 1
See the answer to the preceding question (12:29:2.3:1) as to what this indicates.
Rashi writes: "'Mi'Bechor Pharaoh' - Pharaoh himself was also a Bechor, and yet he remained [alive] from Makas Bechoros...." Why not explain the verse simply as "the firstborn of Pharaoh," i.e. that the crown prince was hit by the Makah (as indeed Rashbam explains)?
Gur Aryeh #1: Just as "Bechor ha'Shevi" means 'the firstborns among the captives themselves' (as opposed to 'the firstborns of the captive parents'), so too "'Bechor Pharaoh" means 'Pharaoh who was himself a firstborn.'
Gur Aryeh #2: The Mechilta explains the following phrase, "... who would sit upon his throne," as referring to the crown prince. This phrase, must then refer to Pharaoh himself. 1
Gur Aryeh: Nevertheless, we make no derivation from the parallel phrases regarding location - "[the captive] who is in the dungeon;" or "[the maidservant] who is behind the mill" (11:5). These phrases are merely for parallel structure..
Rashi writes: "'Mi'Bechor Pharaoh' - Pharaoh himself was also a Bechor." But in the warning (11:5), the same phrase appeared, and Rashi did not interpret this way?
Gur Aryeh #1: Rashi explains "Bechor Pharaoh" in our Pasuk , such that it will parallel the phrase "Bechor ha'Shevi" 1 - which appears in this Pasuk only. Pasuk 11:5, on the other hand, says "Bechor ha'Shifchah," which means, 'the firstborn son of the maidservant; so "Bechor Pharaoh" in that context would mean 'the firstborn [son] of Pharaoh.'
Gur Aryeh #2: It would not be an effective warning to tell Pharaoh, 'All the firstborn will die, except for you yourself, Pharaoh. Despite being a firstborn, you will be spared.' Obviously, there would be no hint of this in 11:5.
See above, 12:29:3.1:1.
Rashi writes: "'Mi'Bechor Pharaoh' - Pharaoh himself was also a Bechor." According to Maharal, what does this indicate conceptually?
Maharal (Gevuros Hashem Ch. 37, p.140): The Egyptians primary power was their firstborn; they worshipped Mazal Taleh, the first of the twelve zodiac constellations. 1 In order to subjugate Yisrael, Pharaoh had to excel in the power of Egypt - i.e. to be a firstborn himself. 2
Maharal: The Mitzrim were base Chomer; and Chomer is first in relation to Tzurah (for explanation of Maharal's terminology, refer to 12:12:7.6:3*).
In other words, to put Egypt at full force, their king had to be an expression of the root of their power. Hashem likewise calls Bnei Yisrael, "Beni Bechori" (4:22); for more on the distinction between Yisrael as a firstborn and the Egyptian firstborn, refer to 12:30:2.1:1, 12:13:2.4:1**, 12:12:2.2, and 8:22:1.2:1.
Rashi writes: "... About this it is said, '[Nevertheless, it is for this that I have kept you alive], in order to show you My might' (9:16) - at the Sea." But the context of that verse is the plague of hail, and the plagues in general!
Gur Aryeh: In introducing the plague of Barad, Hashem says "For I [could have] ... smitten you and your nation with Dever" (9:15). He continues, "Nevertheless, it is for this that I have kept you alive, in order to show you My might..." (9:16) - here, only Pharaoh is mentioned, and the term "your nation" is glaringly absent. This alludes to Makas Bechoros, in which Pharaoh was the only firstborn that survived. 1
That verse then means, 'I preserved the lives of the Egyptians in general, from Dever and other Makos [prior to Makas Bechoros], and the life of Pharaoh [even from Makas Bechoros] -- all in order to show them My power.'
Rashi writes: "'Until the firstborn captives' - For they would rejoice at the misfortune of Yisrael; and also, so that they would not claim that their deity had brought this calamity upon Egypt." Why are both of these two reasons necessary?
Gur Aryeh: The second reason alone is insufficient, it does not explain what these foreigners did to deserve such punishment. The first reason alone is also insufficient, for while rejoicing at another's misfortune is sure to have some consequence, Makas Bechoros came only to bring the Redemption for Yisrael. Because it had this element of debunking idolatry, it was indeed part of the Redemption.
Rashi writes: "Va'Shem - Whenever [this term] is used, [it means,] 'He and His [Heavenly] court;' as the letter Vav implies 'in addition to.'" But Rashi wrote above (to 12:12), and the Hagadah teaches, that Hashem alone carried out Makas Bechoros - to the exclusion of any angel or messenger?
Moshav Zekenim (to 12:12): The Torah means that Hashem's Beis Din - even Midas ha'Rachamim - agreed to Makas Bechoros, but it was Hashem alone who killed them.
Gur Aryeh: Hashem performed the essence of Makas Bechoros, taking the essential life (Ikar Nefesh) of the firstborn. His court took a secondary role, striking peripherally. 1
What was that role; who or what did the Heavenly court strike? Refer to 12:12:7.3:1*.
Rashi writes: "Va'Shem - ... Whenever [this phrase] is used, [it means] 'He and His [Heavenly] court.'" Mizrachi (to 12:12) asks - How then can we resolve the verse, "Va'Shem Himtir Al Sedom, etc." (Bereishis 19:24)? Weren't two angels given the task to overturn Sedom?
Gur Aryeh: That verse tells us that on that occasion, first Hashem and His Heavenly court rained down sulfur and fire upon Sedom (19:24). Afterwards, the two angels overturned the cities (19:25) - which was a separate stage of the punishment.