John Calvin Commentary Isaiah 19:6

"And the rivers shall become foul; the streams of Egypt shall be diminished and dried up; the reeds and flags shall wither away." — Isaiah 19:6 (ASV)

And the brooks of defence shall be emptied and dried up. What he adds about fortifications is consistent with what he had stated immediately before. He alludes to the embankments, which not only restrained the overflowing of the Nile but also protected the whole country; it is as if he had said that the embankments would not be needed because the Nile would be dried up.

Now, it is certain that the Nile was not actually dried up, and yet the Prophet did not foretell something that was not accomplished.

We must therefore recall what we have already said: because of our stupidity, these calamities are vividly represented to us, placing them, so to speak, before our very eyes. This is because we need a portrayal that is suited to impress our minds and to arouse us to consider God's judgments, which we otherwise despise.

We should observe the haughtiness of the Egyptians, whose resources were so various and abundant, and who thought it was impossible for them to be overtaken by such a calamity.