מדרש אויף שמות 9:18

“Behold, I will rain down tomorrow at this time very severe hail, that there has not been like it in Egypt since the day it was founded until now” (Exodus 9:18).
“Behold…tomorrow at this time…very severe hail.” Zavdi ben Levi said: He scratched a mark on the wall. He said to him: ‘When the sun reaches here, the hail will fall tomorrow.’ “That there has not been like it in Egypt” – to tell you that there had not been like it in the world and not in Egypt. It does not say that there will not be like it, like it said about the plague of the firstborn: “Nor will be like it any more” (Exodus 11:6). “That there has not been like it” – in other words, in the past there has not been, but there is destined to be in the future. When? In the days of Gog and Magog; that is what is written: “Which I have reserved for a time of trouble, for a day of battle and war”³The previous verse concludes with a mention of storehouses of hail. (Job 38:23), and so it says: “Torrential rain and hailstones” (Ezekiel 38:22).
“Now, send and gather your livestock and everything that is yours in the field; every man and animal that will be found in the field and will not be gathered into the house, the hail will fall upon them and they will die” (Exodus 9:12).
“Now send, and gather your livestock” – come and see the mercy of the Holy One blessed be He; even at the time of His anger, He had mercy on the wicked and on their animals, as He did not send the plague of hail upon them, but only on the crops of the land. He cautioned them that they preserve themselves and their animals, so they would not be stricken with the hail.
He who feared the word of the Lord among the servants of Pharaoh drove his servants and his livestock into the houses. And he who disregarded the word of the Lord, he left his servants and his livestock in the field (Exodus 9:20-21).
“He who feared the word of the Lord among the servants of Pharaoh.” Our Rabbis, of blessed memory, said: That was Job; “and he who disregarded,” that was Pharaoh, and his people.

Behold, tomorrow about this time I will cause it to rain a very grievous hail, such as hath not been seen (Exod. 9:18). Zabdi the son of Levi said: He made a mark upon the wall and told him that when the sun reached that mark tomorrow, the hail would fall. Such as hath not been seen implies that it would be a hail like none that had occurred previously, and would occur again only in the days to come, that is, in the time of Gog and Magog, as it is said: Which I have reserved against the time of trouble, against the day of battle and war (Job 38:23). It also says: And I will plead against him with pestilence and with blood; an overflowing shower and great hailstones (Exod. 38:22). And now therefore send, hasten in thy cattle (ibid. 9:19), on account of the plague of hail. He said to him: Wicked one, the Lord is righteous indeed.

(Exod. 9:18:) BEHOLD, AT THIS TIME TOMORROW I WILL RAIN DOWN <VERY HEAVY HAIL>. Zavday ben Levi said: He scratched a single mark for him on the wall.¹¹⁰Tanh., Exod. 2:16; Exod. R. 12:2. He said to him: Tomorrow when the sun reaches here, I will bring hail down upon you. (Ibid., cont.:) SUCH AS HAS NEVER BEEN. Nothing has happened like it, but it is going to happen to the nations. It is prepared for Sennacherib. <These are> the words of R. Simon. R. Hanina said: It is prepared for the punishment of Gog and Magog, as stated (concerning Gog in Ezek. 38:22): AND I WILL POUR TORRENTIAL RAIN, HAILSTONES, <FIRE, AND BRIMSTONE UPON HIM AND HIS HOSTS AND THE MANY PEOPLES THAT ARE WITH HIM>.¹¹¹On Gog and Magog, see above, note 68.