The staff is not mentioned in this verse, but it is understood that Aaron was holding his staff when he stretched out his hand. The waters of Egypt includes all the bodies of water mentioned in verse 5. As in 7.19, however, such an act was a symbolic gesture and should not be understood literally. Good News Translation‘s “all the water” simply translates the waters of Egypt; the word “all” is not in the Hebrew. It is possible to simplify So Aaron stretched out his hand over … by saying “Aaron obeyed Moses, and the frogs….”

And the frogs came up has the same verb as in verse 5, meaning to come up out of the water. So Good News Translation has “and the frogs came out.” Here the word frogs is singular in form, followed with the singular verb covered. This emphasizes the idea of a swarm or horde of frogs so great that it completely “covered over” the land of Egypt. (This collective singular form is also used for the “flies” in 8.21 and the “locusts” in 10.4.)

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .