Charles Ellicott Commentary Exodus 7:20

"And Moses and Aaron did so, as Jehovah commanded; and he lifted up the rod, and smote the waters that were in the river, in the sight of Pharaoh, and in the sight of his servants; and all the waters that were in the river were turned to blood." — Exodus 7:20 (ASV)

He lifted up the rod. —“He” is, undoubtedly, Aaron. (See Exodus 7:19.)

In the sight of Pharaoh, and in the sight of his servants. —If the occasion was one of a Nile festival, Pharaoh would have gone out to the water (Exodus 7:15) accompanied by all the great officers of the Court, by a large body of the priests, and vast numbers of the people. If it was a mere occasion of bodily ablution, he would have had with him a considerably numerous train of attendants. In either case considerable publicity was given to the miracle, which was certainly not “done in a corner.”