Exodus 7:20

“And Moses and Aaron did so, as the Lord commanded, etc.] Moses delivered the rod to Aaron, who took it and went to the water side: and he lift up the rod, and smote the waters that were in the river; or “in that river” f206, the river Nile, on the brink of which Pharaoh then stood: in the sight of Pharaoh, and in the sight of his servants; his nobles and courtiers who tended him in his walk to the water; for this was done before he returned to his palace: and all the waters that were in the river were turned into blood; not only the face of the waters looked like blood, but they were really turned into it; and not only the surface of the water, but all the water that was in the river,…”

“The waters that were in the river were turned into blood - This was a plague justly inflicted upon the Egyptians; for Nilus the river of Egypt was their idol; they and their land had so much benefit by that creature, that they served and worshipped it more than the creator. Also they had stained the river with the blood of the Hebrew children, and now God made that river all bloody; thus he gave them blood to drink, for they were worthy, Rev 16:6. See the power of God. Every creature is that to us which he makes it to be, water or blood. See the mutability of all things under the sun, and what changes we may meet with in them. That which is water to day may be blood to morrow; what is always…”

“he lifted: Exo 17:5, Exo 17:6, Exo 17:9-12; Num 20:8-12 all the waters: As the Nile was held sacred by the Egyptians, as well as the animals it contained, to which they annually sacrificed a girl, or as others say, both a boy and girl, God might have designed this plague as a punishment for such idolatry and cruelty; and to shew them the baseness of those elements which they reverenced, and the insufficiency of the gods in which they trusted. All the punishments brought upon them bore a strict analogy to their crimes. Exo 7:17, Exo 7:18; Psa 78:44, Psa 105:29; Joh 2:9-11; Rev 8:8 Exodus 7:21”