וְהַדָּגָ֧ה אֲשֶׁר־בַּיְאֹ֛ר תָּמ֖וּת וּבָאַ֣שׁ הַיְאֹ֑ר וְנִלְא֣וּ מִצְרַ֔יִם לִשְׁתּ֥וֹת מַ֖יִם מִן־הַיְאֹֽר׃ (ס)
And the fish that are in the river shall die, and the river shall become foul; and the Egyptians shall loathe to drink water from the river.’
Read Jewish philosophical commentary on Exodus 7:18: and classical philosophical sources.