Matthew Henry Presbyterian @wholebiblehenry

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.

Commenting on Exodus 7:14-25

John Gill Reformed Baptist @doctorgill

And seven days were fulfilled,.... Or there were full seven days, a whole week: after that the Lord had smitten the river, and turned it into blood; here the miracle is ascribed to him; Moses and Aaron, and the rod they used, were only instruments, nothing short of almighty power could do such a miracle; it seems this lasted seven days at least.

Adam Clarke Methodist @methodicalclarke

And seven days were fulfilled - So we learn that this plague continued at least a whole week. The contention between Moses and Aaron and the magicians of Egypt has become famous throughout the world. Tradition in various countries has preserved not only the account, but also the names of the chief persons concerned in the opposition made by the Egyptians to these messengers of God.