Charles Ellicott Commentary Isaiah 48:4

"Because I knew that thou art obstinate, and thy neck is an iron sinew, and thy brow brass;" — Isaiah 48:4 (ASV)

Because I knew that you are obstinate ... —The point is that Jehovah foresees not only the conquests of Cyrus, but the obstinacy of His own people. In Egypt (Jeremiah 44) and in Babylon, as in the past, they were still a stiff-necked people, inclined (Isaiah 48:5) to ascribe their deliverance to another god, and to worship that god in the form of a graven image.