Isaiah 11:15 - Matthew Poole's English Annotations on the Holy Bible

Shall utterly destroy; shall not only divide it, as of old, but will quite dry it up, that it may be a highway, as it is explained in the next verse. The tongue of the Egyptian sea; the Red Sea, which may well be called the Egyptian sea, both because it borders upon Egypt, and because the Egyptians were drowned in it, which is called a tongue in the Hebrew text, Joshua 15:2,5, as having some resemblance with a tongue; for which reason the name of hath been given by geographers to promontories of land which shoot forth into the sea, as this sea did shoot out of the main ocean into the laud. Shake his hand; he alludes to Moses's shaking of his hand with the rod of God in it over the sea; over the river, to wit, of Egypt, Nilus, as appears both from the foregoing and from the following words. The seven streams; for which Nilus is famous in all authors, and by which it emptieth itself into the sea.