Don't rebel against Assyria. Don't turn to Egypt for help. Trust YHWH.
That is a vest pocket account of at least some of Isaiah's preaching. I can see why the leaders of Jerusalem dismissed the prophet's message as childish gobbledygook (Isaiah 28:9-10). It might have been easy to write Isaiah off as naive. Mad even. Surely he didn't understand international politics. The pragmatist might say "Trust God but row for shore." Isaiah was no pragmatist. His motto could have been "YHWH take the wheel!"
Curiously, Isaiah seems to have read the situation correctly. Egypt was no help. The Assyrian campaign against Jerusalem was called off.
Isaiah 31 reiterates the themes of chapter 30. Turning toward Egypt is an act of treason against YHWH. The Lord himself will destroy Assyria.
The Harper Collins Study Bible states that Isaiah 31:6-7 are a "call to repentance originally addressed to the Northern Kingdom." If so, these words are out of place:
Return, you Israelites, to the One you have so greatly revolted against. For in that day every one of you will reject the idols of silver and gold your sinful hands have made.
The Jewish Study Bible notes seem to assume that these verses are addressed to Judah.
This is the first passage in which Isaiah calls on the nation to repent since 6. 9, where God ordered Isaiah not to engender penitence among the Judeans.
The Judahites were, arguably, also Israelites.
Chapter 32, verses 1-20 describe the justice and righteousness that will exist when an ideal king rules presumably at the "end of days." In verses 9-15 the prophet addresses the women of Jerusalem a little more respectfully than he did in 3:16-4:1. The women are complacent and their city will be devastated. Isaiah calls them to repent and promises prosperity.
Chapter 33 brings the prophecies of First Isaiah to an end. YHWH will defeat Assyria. Only the righteous will live in Jerusalem.
Chapter 34 is an oracle ostensibly addressed to "all nations."
The LORD is angry with all nations;
his wrath is on all their armies.
He will totally destroy them,
he will give them over to slaughter.
Very quickly, however it narrows its focus down to Edom. Things will not go well for Edom. It will become a desert, a haunt for unclean wild beasts and demons.
The desert owl and screech owl will possess it;
the great owl and the raven will nest there.
God will stretch out over Edom
the measuring line of chaos
and the plumb line of desolation.
Her nobles will have nothing there to be called a kingdom,
all her princes will vanish away.
Thorns will overrun her citadels,
nettles and brambles her strongholds.
She will become a haunt for jackals,
a home for owls.
Desert creatures will meet with hyenas,
and wild goats will bleat to each other;
there the night creatures will also lie down
and find for themselves places of rest.
The New Revised Standard Version and the Jewish Publication Society Tanakh version translate that last verse to include "goat-demons" and the "lilith" (a "kind of demon" according to a textual note in the JPS Bible).
While all of this is bad news for Edom, it is good news for Judah. Chapter 35 tells how the desert where Edom once stood will blossom as the Judahites, in a new exodus, return from their Babylonian captivity on a miraculous highway. There may be a little prophetic hyperbole here.
Scripture quotes are still coming from the New International Version, though I'm not always sure why.
Next: Isaiah 36-41