Midras Keluaran 9:3: Ruth Rabbah, Mekhilta DeRabbi Yishmael, Midrash Tanchuma & Bamidbar Rabbah

Rabbi Levi said: Any place where [the phrase] “the hand of God” is stated, it is the plague of pestilence. The paradigm of them all is: “Behold, the hand of the Lord is [upon your cattle… a very severe pestilence]” (Exodus 9:3). Bar Kappara said: They demanded with the hand,¹¹⁴“Would that we had died by the hand of God in Egypt” (Exodus 16:3). and the hand¹¹⁵Regarding the generation of the wilderness, it is written: “And the hand of God was against them…until their demise” (Deuteronomy 2:14–15). harmed them. Rabbi Simon said: Among those who departed [the land of Israel] there was a plague;¹¹⁶This is derived from the fact that it states here: “The hand of the Lord has emerged against me [yatze’a bi],” which can be interpreted in the sense of biyatzi, “when I left.” among those who remained there was no plague. The students of Rabbi Neḥemya cite it from there: This is what is written: “Wherever they departed, the hand of the Lord was against them for evil” (Judges 2:15) – among those who departed there was a plague; among those who remained there was no plague. Rabbi Reuven said: Their children,¹¹⁷The children of those who departed Egypt. too, were suffering in their wake, and saying: ‘When will they die so we can enter the Land?’

(Exodus 14:7) "And he took six hundred choice chariots": Whence came the horses required for the chariots? If you would say, from Egypt, is it not written (re the plague of pestilence, Ibid. 9:6) "and all the cattle of Egypt died"? And if you would say, from Pharaoh, is it not written (Ibid. 3) "Behold, the hand of the L–rd is in your cattle in the field, in the horses, etc."? And if you say, from Israel, is it not written (Ibid. 10:26) "And our cattle, too, will go with us; not a hoof will remain"? Whence, then, did they come? From those (of his servants) who feared the word of the L–rd (viz. 9:20) and drove his horses from the field into the houses. We find, then, that the cattle driven off by those who feared the word of the L–rd proved to be an impediment to Israel — whence R. Shimon says: "the best of the gentiles — kill! The best of the serpents — crush its head!"

They forced the Israelites to pasture their flocks, and so he sent the murrain against them, as it is said: Behold, the hand of the Lord is upon thy cattle (Exod. 9:3). They compelled the Israelites to keep the heated things warm, and so He afflicted them with boils. They plotted to have them stoned to death and so He sent hail upon them. They planned to make the Israelites their gardeners, and so He brought against them the locusts, which consumed their trees, and ate all the grass and fruit in the land. They conspired to imprison them, and so He brought darkness upon them. They planned to kill the Israelites, and so He smote all their firstborn. They wanted to drown them in water, and so He overthrew Pharaoh and his host in the Red Sea (Ps. 136:15).