And the LORD said to Moses, “Tell Aaron, ‘Take your staff and stretch out your hand over the waters of Egypt—over their rivers and canals and ponds and all the reservoirs—that they may become blood.’ There will be blood throughout the land of Egypt, even in the vessels of wood and stone.”
19. And the Lord spake unto Moses. This is the more extended narrative of which I spoke; for Moses mentions nothing different from what went before, but explains more distinctly his mode of action in the performance of the miracle, namely, that what God had commanded was completed by the instrumentality of Aaron.
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
And the Lord spake unto Moses,.... Pharaoh still being obstinate, and refusing to let the people go: say unto Aaron, take thy rod, and stretch out thine hand upon the waters of Egypt; upon all of them in general, what were in the river Nile, or derived from it, as follows: upon their streams; the seven streams of the river Nile; see Gill on Isa 11:15.