“These former things
I declared long ago.
They went out from my mouth.
I made them known.
Then suddenly I did them.
They came to pass.
Because I know
That you are obstinate.
Your neck is an iron sinew.
Your forehead is brass.”
Second Isaiah has Yahweh say that he had declared a long time ago from his own mouth what was going to happen before it suddenly happened. He wanted the hard headed Israelites to know this. However, these obstinate stiff necked people with iron wills and hard brass foreheads ignored this.
Eugene Finnegan Bible Project 