Isaiah 28-30

Ephraim is the Northern kingdom of Israel and God hates the pride there....Isaiah is prophesying Ephraim's punishment.
Verses 9-14 show the people's reaction....they don't feel that they need to be taught and feel that they can make up their own minds.  The people chose to look for protection from other sources, so God tells them they are making a covenant with death. In verses 16-19, the cornerstone is the Messiah, who will deliver and judge with justice.  "The scourge" is going to humble them soon (near and far prophecy)

Ariel is a special name for Jerusalem, just like Zion is...Isaiah has pronounced judgment on the other nations, and now Ariel will be judged for going their own way and not listening to God.  Their worship wasn't pleasing to God because it was empty ritual...after being humbled, those that see the true way will be saved and blessed.

God calls the nation obstinate children because they don't seek Him as savior, but look to foreign powers.  They only want to hear what they want to hear....God longs to be gracious to His children and when they cry for help, He will help them.