John Calvin on Isaiah 19:6

6. And the brooks of defence shall be emptied and dried up. {Bogus footnote} What he adds about fortifications is to the same purpose with what he had stated immediately before. He alludes to the embankments, which not only restrained the overflowing of the Nile, but protected the whole country; as if he had said that the embankments will not be needed, because the Nile will be dried up. Now, it is certain that the Nile was not laid dry, and yet the Prophet did not foretell what was not accomplished. We must therefore call to remembrance what we have already said, that on account of our stupidity those calamities are represented to us in a lively manner, which places them as it were before our eyes; for we need to have a representation made to us which is fitted to impress our minds, and to arouse us to consider the judgments of God, which otherwise we despise. We ought to observe the haughtiness of the Egyptians, whose resources were so various and abundant, and who thought that it was impossible for them to be overtaken by such a calamity.