Albert Barnes 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 the streams of it — The idea here is that there would be as great and awful a destruction as if the streams everywhere were to become pitch or resin, which would be set on fire and fill the land with flame. This image is very striking, as we can see by imagining the rivers and streams in any land flowing not with water, but with heated pitch, turpentine, or tar, and all of this suddenly kindled into a flame.

It should not be supposed that this is to be taken literally. The image is evidently taken from the destruction of Sodom and Gomorrah (Genesis 19:25–28), an image which is more fully used in reference to the same subject in Jeremiah 49:17-18: And Edom shall be a desolation;... as in the overthrow of Sodom and Gomorrah, and the neighbor cities thereof, saith the Lord, no man shall abide there, neither shall a son of man dwell in it.

And the dust of it into brimstone — The ruin will be as entire as if all the soil were turned into brimstone, which would be ignited and left burning.