Because I knew that thou art obstinate... — The point is that Jehovah foresees not only the conquests of Cyrus, but the obduracy of His own people. In Egypt (Jeremiah 44) and in Babylon, as of old, 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.
Related Commentaries of Isaiah 48:4
Isaiah 48:4
4 Because I knew that thou art obstinate,a and thy neck is an iron sinew, and thy brow brass;