Isaiah 31 - The Lord Will Defend Jerusalem

I. Rationale for Trust (1-3)

Judah trusted the Egyptian because of their strength and their numbers. But they do not look to the Lord because they can't find the rational reason to.  David said the contrary: "Some trust in chariots, and some in horses; but we will remember the name of the LORD our God." (Ps 20:7) 

However, they forgot that the Egyptians are merely men, and not God; the horses are only flesh and not spirit. God just need to stretch out His hands and both Egypt and those they help will fall. (v2-3)

II. The Lord will save Jerusalem (4-9)

It will not the the Egyptians, but the Lord Himself will defend Jerusalem. (v5).  Judah is asked to return to God and cast away their idols. Assyria itself will fall not from the sword of men, but the sword of God. (v8)