This chapter contains two distinct messages. In the first, the prophet denounces an alliance with Egypt (verses Isaiah 30:1-26), and in the second foretells the destruction of Assyria (verses Isaiah 30:27-33).
In the matter of the Egyptian alliance the prophet denounces the secret treaty, declares the shame and uselessness of it. He is instructed to write what shall be a testimony against the people. This he does by first describing the rebellious attitude which they have adopted, then by declaring how Jehovah will break in pieces the things in which they trust, and, finally, by indicating what their true attitude should have been, and declaring their refusal to adopt it and their consequent discomfiture. Yet the intention of Jehovah is gracious, and He waits for them until they are restored to the spirit of willingness, and are ready to sweep out idolatry. In answer to this, they are brought back to prosperity, which is described in its relation to the new glory of the land.
The destruction of Assyria is announced by a description of Jehovah coming in judgment. This will be the occasion for His people to sing a song of rejoicing and deliverance, which will result in completely and relentlessly sweeping away the oppressing nation. This prophecy of the destruction of Assyria at this point was intended to show the people of God how unnecessary it was for them to turn to Egypt for help.
the Week of Proper 20 / Ordinary 25