Moses
Exodus 7:17BSB·traditional attribution

This is what the LORD says: By this you will know that I am the LORD. Behold, with the staff in my hand I will strike the water of the Nile, and it will turn to blood.

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

Thus saith the Lord, in this thou shalt know that I am the Lord,.... By the following instance of his power and vengeance: behold, I will smite with the rod that is in my hand; which though in the hand of Moses, Exo 7:18 yet he being his ambassador, and representing him, is said to be in the hand of the Lord; and with this...

Jamieson-Fausset-Brown Reformed @jfbcommentary

Aaron lifted up the rod and smote the waters, &c.--Whether the water was changed into real blood, or only the appearance of it (and Omnipotence could effect the one as easily as the other), this was a severe calamity. How great must have been the disappointment and disgust throughout the land when the river became of a blood red color, of which they had a...