John Gill Commentary Exodus 8:5

"And Jehovah said unto Moses, Say unto Aaron, Stretch forth thy hand with thy rod over the rivers, over the streams, and over the pools, and cause frogs to come up upon the land of Egypt." — Exodus 8:5 (ASV)

And the Lord spoke to Moses
By a secret impulse upon his mind, for he was now in the presence of Pharaoh, who had refused to let Israel go:

say to Aaron, stretch forth your hand with your rod ;
for Aaron carried the rod, and he was the minister of Moses, who was appointed a god to him; and he was to speak and to do whatever he ordered him from the Lord:

over the streams, over the rivers and over the ponds ;
the seven streams of the river of Nile, and over the canals cut out of it, and over all places where there was a collection of water for any use for man or beast:

and cause frogs to come up upon the land of Egypt ;
out of the streams, rivers, and ponds, immediately.