John Gill Bible Commentary

He turned their waters into blood,.... With which Egypt abounded; their streams, rivers, ponds, and pools, so that they had no water to drink; a just judgment upon them for shedding the innocent blood of infants, by drowning them in their rivers; this was the first of the ten plagues, Exo 7:19, with this compare the second and third vials poured out on spiritual Egypt, whereby blood will be given to antichrist, and to the antichristian states, for they are worthy, having shed so much of the blood of the saints, Rev 16:3. And slew their fish; which showed that the miracle was real, that the waters were really turned into blood, since the fish could not live in them, as they might if it had been only in appearance; the rivers of Egypt abounded with fish, this was a principal part of their food, and therefore must greatly distress them; see Num 11:5.