Isaiah 30

Anytime a crack appears in a support wall it is reason for concern. The crack tells a story. It not only speaks of the impending failure of the wall it points accusing fingers at those this that led to the crack. There is the foundation that gave up support first and also the load that bears down on the top. The crack can also display the indifference of the builders' attention to quality or their inexperience in construction techniques. The crack also speaks bleakly about the future of the wall in which it develops. And that was the point Isaiah was making in verse 13. Judah is a cracked wall. Their sin will lead to their downfall.
Stuart