John Calvin Commentary Isaiah 34:9

"And the streams of [Edom] shall be turned into pitch, and the dust thereof into brimstone, and the land thereof shall become burning pitch." — Isaiah 34:9 (ASV)

And its streams shall be turned into pitch. What the Prophet now adds contains nothing new, but describes this desolation more fully. We have previously explained why the prophets employ these vivid descriptions in representing the judgments of God. Its purpose is to lead people to view them as actually present and to compel them to acknowledge those things that their eyes and minds do not perceive, or that, as soon as they are seen and known, are immediately forgotten.

But it should also be observed that the Prophets spoke of things that were obscure and secret, and which were generally thought to be unbelievable, for many people imagined that the Prophets uttered them at random. It was, therefore, necessary to add many confirmations, such as those which he employs in this and in other passages; and thus he indicates a horrible change, which will destroy the whole face of Judea.

Moreover, he alludes to the destruction of Sodom and Gomorrah (Genesis 19:24), as the prophets very frequently do. In that destruction, as Jude informs us, we have a perpetual representation of the wrath of God against the reprobate (Jude 1:7); and it is not without good reason that the prophets remind us of it, so that all may learn to dread the judgments of God. To the same purpose is what he adds—