Exodus 7:17

“Thus saith the Lord, in this thou shalt know that I am the Lord, etc.] 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, (<020718>Exodus 7:18) yet he being his ambassador, and representing him, is said to be in the hand of the Lord; and with this he threatens to smite upon the waters which are in the river; the river Nile, and the canals thereof: and they shall be turned to blood; and if this river was their god, it would abundantly appear that the God of the Hebrews was Jehovah, and above all gods, and particularly above theirs.”

“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 national abhorrence; their favorite beverage became a nauseous draught, and the fish, which formed so large an article of food, were destroyed. [See on Num 11:5.] The immense scale on which the plague was inflicted is seen by its extending to "the streams," or branches of the Nile--to the "rivers," the canals, the "ponds" and "pools," that…”

“Turned to blood - This miracle would bear a certain resemblance to natural phenomena, and therefore be one which Pharaoh might see with amazement and dismay, yet without complete conviction. It is well known that before the rise the water of the Nile is green and unfit to drink. About the 25th of June it becomes clear, and then yellow, and gradually reddish like ochre; an effect due to the presence of microscopic cryptogams and infusoria. The supernatural character of the visitation was tested by the suddenness of the change, by its immediate connection with the words and act of Moses, and by its effects. It killed the fish, and made the water unfit for use, neither of which results follows…”

“thou shalt: Exo 7:5, Exo 5:2, Exo 6:7; Sa1 17:46, Sa1 17:47; Kg1 20:28; Kg2 19:19; Psa 9:16, Psa 83:18; Eze 29:9, Eze 30:8, Eze 30:19, Eze 32:15, Eze 38:23, Eze 39:28; Dan 4:17, Dan 4:32, Dan 4:37, Dan 5:21, Dan 5:23 and they: Exo 1:22, Exo 4:9; Psa 78:44, Psa 105:29; Rev 8:8, Rev 16:3-6 Exodus 7:18”