He will send you all away. [Rashi is explaining that כלה is] not from the word כלייה (destruction). Rather it is like כליל תקטר (Vayikra 6:15), which Onkelos translates as גמירא (completely burnt). And there, גמירא cannot mean “destruction,” rather it means “completely.”

נא can only indicate. . . Rashi means that נא written here can only indicate pleading [but in other places it can mean “now”].

Speak to them about this. . . You might ask: Since Hashem told it to Moshe, is it not obvious that he will tell it to B’nei Yisrael? The answer is: Moshe did not intend to instruct them about this because [if they fail to return the borrowed items] it will be like holding stolen property. However, Hashem considered it as having received wages for their work (Sanhedrin 91a). Another answer: [Moshe was concerned that] the Egyptians will be troubled by the loss of their property and will chase after them. Therefore, Moshe needed to be told to instruct them.

While still standing before Pharaoh. . . You might ask: Earlier (11:1), it says similarly: “Hashem said to Moshe, ‘There is one more plague. . .’” Furthermore, “I will not see your face again” was written previous to it. Why then did Rashi not make a similar comment there? The answer is: The content of the earlier verse (11:1) was actually told to Moshe before, for it is written (3:21): “I will give this people grace. . .” But it is merely repeated here, because now was the time for its fulfillment. This section, in contrast, is dealing with the exodus from Egypt, and that the plague will be at midnight, was not hinted anywhere else. Perforce, this prophecy was told to Moshe while still standing before Pharaoh. You might ask: If Moshe would not even offer a simple prayer within the city, how could he be given a full prophecy there [see Rashi 11:1]? The answer is: [Hashem did it] for Moshe’s honor so that he should not be considered a liar. Otherwise, Moshe would need to go back to Pharaoh [to announce Hashem’s prophecy, but Moshe had already told Pharaoh that he would not see his face again]. Alternatively: Hashem lifted Moshe ten handbreadths above the ground when He spoke to him, thus placing him in a separate domain. (Re”m)

For חצות is not the noun. I.e., [Rashi is telling us that the term] חצות here is not a noun like it is in (Tehillim 119:62), “ חצות לילה (Inthe middle of the night) I will rise to praise You.” Here this is not so, because it is preceded by a כ , which is not appropriate for a noun. Furthermore, כחצות implies uncertainty as to when midnight is, and surely, Hashem has no such doubt! Thus כחצות must mean, “When the night is divided.”

Which implies at about midnight. . . I.e., our Sages say that חצות here is indeed a noun, meaning “the middle of the night.” Hashem told Moshe בחצות הלילה , meaning exactly at midnight, but — lest Pharaoh’s stargazers say, “Moshe is a liar!” —Moshe changed it to כחצות , meaning at about midnight

And say, “Moshe is a liar!” You might ask: Why should Moshe change Hashem’s words just so these fools will not err? The answer is: From the third plague on, the sorcerers admitted to the authenticity of Moshe’s prophecy. Thus Moshe feared that a desecration of Hashem’s Name might occur at the very conclusion, lest they err now and they will deny the previous prophecies. (Rabbeinu Bechayeh)

Why were the captives struck down? You might ask: The verse mentions the first-born of the captives only later (12:29), in connection with the plague itself. Why does Rashi explain it here [in connection with the warning]? An answer is: Rashi explained above, according to our Sages, that Moshe said “about midnight” because Pharaoh’s sorcerers might say that he is a liar. Yet we might object: Here, they surely will say that Moshe lied! For Moshe said [in his warning], “From the first-born of Pharaoh. . . to the first-born of the [Egyptian] slave girl,” including everyone in between, but excluding those lowlier than the slave girl. Yet later on, in connection with the plague itself, it is written that also the captives were smitten, and they are lowlier, as Rashi explains there. Thus Rashi explains here why the first-born of the captives were struck down, to answer the above objection. [The sorcerers would not err] because they knew that Moshe warned only regarding those who oppressed B’nei Yisrael — i.e., the first-born of Pharaoh until the first-born of the slave girl. But Moshe’s warning did not include the captives. [For the plague came primarily to punish those who enslaved B’nei Yisrael, and] the captives did not enslave them. [As Rashi explains, they died only so that they should not say, “Their own god. . . brought retribution upon the Egyptians.”] Nevertheless, [we could object to the above explanation:] Moshe did not say clearly that the captives are excluded, for the term “first-born of the Egyptian slave girl” could be referring to “the lowly ones,” including the captives. Thus another answer is: Rashi is defending what he explained above, that Moshe changed Hashem’s word because of what the sorcerers might say. If we object that this is no reason to change Hashem’s word, Rashi answers us: “Why were the captives struck down? . . .So they should not say. . .” Thus we see that the captives did not really deserve this, as they did not oppress B’nei Yisrael, and were struck down only because of what they might say. And Moshe changed Hashem’s word for the same reason.

Because they too enslaved them and rejoiced in their oppression. Enslavement alone is not sufficient reason, as it was not a complete enslavement. And rejoicing alone is not sufficient reason, for no action was involved. Thus both reasons are needed. (Maharshal)

Together with all the people. Rashi is answering the question: Why should Pharaoh care if only Moshe leaves? Furthermore, even if he leaves with all the people, but they only leave the city to worship and then return, [why should Pharaoh care]? Therefore Rashi [further] explains, “From your land.”

But only after concluding his words. Moshe left after concluding the whole section of “About the time of midnight. . .” Although Pharaoh had told Moshe to leave [earlier], Moshe did not leave.

Because Pharaoh had said to him, “Do not see my face again!” Rashi is answering the question: On the contrary, should not Pharaoh have been angry with Moshe, for warning him and speaking harshly to him? Therefore Rashi explains, “Because he had said to him. . .”

The killing of the first-born. . . This raises a difficulty: It is written, “In the land of Egypt,” but these wonders were outside of Egypt. (Nachalas Yaakov)