Exodus 11:4

And Mosheh spake (or, had spoken) to Pharoh, Thus saith the Lord, At this hour of the following night will I be revealed in the midst of the Mizraee,

AND MOSES SAID: THUS SAITH THE ETERNAL: ABOUT MIDNIGHT WILL I GO OUT INTO THE MIDST OF EGYPT. Moses said this to Pharaoh and to his servants, as he mentioned at the end of his words, And all these thy servants shall come down unto me. Now he did not explain on what night this plague will take place, since this Divine communication to Moses and the transmission thereof to Pharaoh happened before the first of Nisan, the first of Nisan. In my opinion, this is to be explained on the basis of that which Ramban wrote in Seder Shemoth (4:21), that at the very first time that Moses came before Pharaoh, he warned him of the last plague which will force him to let the people go. In that case, the Divine communication to Moses and the transmission of it to Pharaoh did indeed take place before the first of Nisan. The verse here, yet one plague more will I bring upon Pharaoh, must then be understood in the sense that G-d told Moses that the time had come for the final plague of which He had told him in the beginning and which Moses had related to Pharaoh. See also my Hebrew commentary, p. 323, for further discussion of this problem. and when he said about midnight, he did not yet know on which night it would be. Thus Moses did not inform them of the specific night on which this plague would take place, but instead he said in kindled anger, “I will see thy face again no more. It is you who will call upon me at about midnight to go out from your country, and your servants will bow down to me.” In the second section He elucidated to Israel, And I will go through the land of Egypt in that night, and in the third section Scripture states, And it came to pass at midnight,, Verse 29. i.e., the night mentioned when they were eating the paschal lamb.

'ויאמר משה לפרעה כה אמר ה' כחצות הלילה, וגו, the construction of כחצות is derived from the root חצה just as כעשות is derived from the root עשה, or as in the expression כעלות המנחה the word כעלות is derived from the root עלה. In other words, the meaning of כחצות הלילה is: “as soon as midnight arrives.” אני יוצא בתוך מצרים, when it came to the execution of this prophecy the Torah writes instead: ויהי בחצות הלילה, “it was exactly at midnight.” (12,12). This is the plain meaning of the text. The reason Moses had to use a slightly different formulation was that he meant to say that G’d will divide the night into 2 halves, יחצה. Seeing that the word כחצות describes an activity by G’d being performed at a certain time, Moses could not merely have described the time without avoiding reference to G’d doing something at that time.

כחצות הלילה, “around midnight, etc.” G–d brought on the plagues on Egypt according to norms familiar to kings of flesh and blood. When a nation disobeys its ruler, the first thing such a ruler does is to interfere with its water supply. This is why Good first interfered with Egypt’s water supply, turning it into blood. When this proved ineffective, He resorted to frighten them by noises; in order to achieve this he had the frogs which are extremely noisy invade every part of the Egyptians’ homes, including their most private rooms. When this also proved useless, He subjected them to pricks such as are caused when a person is struck by arrows. The vermin did this to the skin of the Egyptians. Following the failure of achieving his objective, He subjected civilised Egyptians to barbarians, i.e. to hordes of ferocious animals whose normal habitat was elsewhere. The next step was to strike their livestock, still not afflicting them with lethal force. They were then subjected to intolerable stench, eventually even immobilised during the plague of darkness. When this proved ineffective, He struck dead both adults and children, i.e. their respective firstborns. Our author quotes verses from different parts of the Bible backing up his claims about frogs being noisy, etc.; etc.;