For all this his anger
See (Isaiah 9:17); (Isaiah 9:21); (Isaiah 5:25); (Isaiah 10:4).
The context explains. Jehovah's hand is outstretched still because His chastisement is followed by no amendment on the part of Israel.
Related Commentaries of Isaiah 9:12
Isaiah 9:12
12 The Syrians before, and the Philistines behind; and they shall devour Israel with open mouth. For all this his anger is not turned away, but his hand is stretched out still.