John Gills Exposition of the Bible Commentary - Exodus 7:21
And the fish that was in the river died ,.... Which was a full proof that the conversion of it into blood was real; for had it been only in appearance, or the water of the river had only the colour of blood, and looked like it, but was not really so, it would not have affected the fishes, they would have lived as well as before; and this plague was the greater affliction to the Egyptians, not as it affected their drink but their food, fish Numbers 11:5 being what the common people chiefly... read more
Matthew Henry's Complete Commentary - Exodus 7:14-25
Here is the first of the ten plagues, the turning of the water into blood, which was, 1. A dreadful plague, and very grievous. The very sight of such vast rolling streams of blood, pure blood no doubt, florid and high-colored, could not but strike a horror upon people: much more afflictive were the consequences of it. Nothing more common than water: so wisely has Providence ordered it, and so kindly, that that which is so needful and serviceable to the comfort of human life should be cheap,... read more