1. I tell you what I have heard from God (1-10)

The Desert by the Sea likely refers to Babylon, whose king (39:1) was in rebellion against Assyria, stirring up Elam and Media in revolt. Many hoped this would liberate them from Sennacherib's power. But the vision wasn't good news! Through the warning of a lookout, Isaiah was shown that Babylon would fall. This likely refers to the destruction of Babylon in 689 BC (Judah's captivity by Babylon was much later, in 586 BC), where their idols' temples were razed and tossed into the sea by Assyria. We cannot trust in nations and their idols, but only in the word of the LORD Almighty.

2. Dumah and Arabia to fall (11-17)

God's hand of judgment through Assyria would reach Israel's ancient relatives: Seir (from Esau), Dumah, Tema and Kedar (from Ishmael, Ge 25) and the Dedanites (of Keturah wife of Abraham Ge 25).