John Calvin Commentary Isaiah 19:5

"And the waters shall fail from the sea, and the river shall be wasted and become dry." — Isaiah 19:5 (ASV)

Then the waters shall fail from the sea. He expands on the subject he had already begun: that the fortifications, by which the Egyptians thought they were admirably defended, will be of no use to them.

They considered themselves to be invincible because they were surrounded by the sea, the Nile, and fortifications. Indeed, historians tell us that it was difficult to enter their land, because the Nile’s mouths were such that they could easily prevent ships from landing.

They therefore boasted that their situation was excellent and that they were strongly fortified by nature, just as the inhabitants of Venice today think that, because they are surrounded by deep ditches, they are impregnable. But fortresses are useless when God has determined to punish us.