מדרש אויף שמות 9:16

And it came to pass in the middle of the night, that the Lord smote all the firstborn in the land of Egypt (Exod. 12:29). The Creator of the night divided the night precisely. The Lord smote all the first born. It was the Lord Himself who smote the firstborn and not His emissary (Moses). In fact, even though a man was elsewhere, and his firstborn was in Egypt, he died. How do we know that the firstborn of the Cuthites, Puthites, and Ludites were also slain? It is said: And smote all the firstborn in Egypt, the first fruits of their strength in the tents of Ham (Ps. 78:51).⁸Ham was the ancestor of Cush, Put, and Lud (Gen. 10:15). Only the firstborn of the Pharaoh remained alive in fulfillment of the verse However, it was for this that I raised you up (Exod. 9:16). And Ba’al Saphon was the only idol remaining, to mislead them, in fulfillment of the verse He increaseth the nations, and destroyeth them (Job 12:23). Unto the firstborn of the captives (Exod. 12:29). Why were the firstborn of the captives punished? Because they had rejoiced in the decrees promulgated against Israel. Hence it is written: He that is glad at calamity shall not be unpunished (Prov. 17:5). You must not be of the opinion that only the captives reacted in that manner, for the slaves and handmaidens did likewise, as is said: Even unto the firstborn of the maidservants that is behind the mill (Exod. 11:5); that is, even those who were legally bound to the millers. Even their firstborn cattle were destroyed lest the people assert: “Our deities are powerful, and that is why punishment was imposed upon them (and not upon us).”

(Exodus 14:28) "And the waters returned and covered the chariot, etc.": even that of Pharaoh. These are the words of R. Yehudah, it being written (Ibid. 15:4) "the chariots of Pharaoh and his host, etc." R. Nechemiah says: except for that of Pharaoh, it being written (Ibid. 9:16) "But, because of this I have preserved you." Others say: Pharaoh descended last and he drowned, viz. (Ibid. 15:19) "For the horse of Pharaoh came with its chariot and its riders into the sea, and the L–rd turned back upon them the waters of the sea."

“The Lord said to Moses: Rise early in the morning, and stand before Pharaoh, and say to him: So said the Lord, God of the Hebrews: Let My people go, and they will serve Me. For this time, I will send all My plagues against your heart and upon your servants and against your people, so that you will know that there is none like Me on the entire earth” (Exodus 9:13-14).
“The Lord said to Moses: Rise early in the morning” – that is what is written: “Behold [hen], God is exalted in His power, who teaches like Him?” (Job 36:22). Rabbi Berekhya said: Hen means one, as in the Greek language, one is called hen. In other words, our God is one. “Exalted in his power” – He increases the strength of the righteous to perform His will. And “who teaches like Him?” – as He teaches the path of repentance. So you find with Moses, whom the Holy One blessed be He strengthened to go on His mission and perform His commands. He taught the wicked Pharaoh to repent because He did not want to send the plague until he forewarns him to [allow him to] repent, as it is written: “Rise early in the morning, and stand before Pharaoh.” He would give Moses strength to rise early and stand before Pharaoh, and he taught the wicked Pharaoh about the path of repentance, as it is written: “And say to him: So said the Lord, God of the Hebrews…. For this time…”
“Why isn’t it stated here “behold, he is going out to the water” (Exodus 8:16)?¹This was the previous place where Moses was instructed to “rise early in the morning and stand before Pharaoh.” Once Pharaoh saw that when he would go out to the water, Moses would precede him on the path, he refrained and did not go out, so that Moses would not encounter him. The Holy One blessed be He said to him: Go to him early, before he leaves his house.
“For I could have now extended My hand and afflicted you and your people with pestilence, and you would be eliminated from the earth” (Exodus 9:15).
“For this time (Exodus 9:14)…For I could have now extended My hand…” The Holy One blessed be He said to him: ‘Woe, wicked one, do you believe that I am unable to eradicate you from the world? Learn from the plague of pestilence. When I sent that pestilence, had I sent it upon you and on your people, you would have been eradicated from the land. However, I only sent it upon you in order to show you the power of My might, and so that you would tell of My strength throughout the land.’ That is what is written: “However, for this I have sustained you [in order to show you My power, and so that My renown will be told of throughout the earth]” (Exodus 9:16).
“You continue to oppress My people, not letting them go” (Exodus 9:17).
“You continue to oppress [mistolel]²The word mistolel is obscure. The midrash understands it to be derived from the root s-l-l, and thus it means literally to cause to be crushed, i.e., in the manner that a road is levelled. Others understand it to be derived from the root s-l-s-l, with mistolel therefore meaning “exalt oneself.” My people.” He would make them like a road [mesila] on which everyone treads, as you say: “…who said to your soul: Bow down, so we may pass, and set down your body like the ground” (Isaiah 51:23).