Charles Ellicott 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 they shall turn the rivers far away. —Better, the river shall stagnate; i.e., in consequence of the Nile’s inundation failing.

The brooks of defence. —The latter noun (Heb., matzor) is better treated as a proper name, the singular of the dual form Mitsraim, commonly used for Egypt. Here it would seem to be used for Lower Egypt, the region of Zoan and Memphis, as distinct from Upper Egypt or the Thebaid. The same form occurs in Isaiah 37:25, 2 Kings 19:24, and Micah 7:12. Its primary meaning is that of a fortified land.

The “flags” are strictly the papyrus of the Nile; the “brooks” are the canals or Nile-branches of the Delta.