Manasseh, Ephraim - This verse is a continuation of the statement in regard to the extent and fearfulness of the faction. Those who were hitherto most tenderly and intimately allied to each other, would now be engaged in furious strife. Manasseh and Ephraim were the two sons of Joseph Genesis 46:20, and their names are used as expressive of tender union and friendship; compare Genesis 48:20. The tribes of Ephraim and Manasseh were near each other, and they always were allied together. The expression here denotes that they who had hitherto been joined in tender alliance, would be rent into contending factions, thirsting for each other’s blood.
And they together - They would be united in opposing Judah while they were devouring each other, as it is not an uncommon thing for those who are opposed to each other to unite in hostility to a common foe; compare Luke 23:12. This is an image that heightens the description of the anarchy - introducing implacable animosity against another tribe, while they were contending among themselves. That such anarchies and factions existed, is apparent from all the history of the kingdom of Israel; compare 2 Kings 15:10 ff; 2 Kings 15:30. In this last passage, the death of Pekah is describer as having occurred in a conspiracy formed by Hoshea.
For all this ... - see Isaiah 9:12, note Isaiah 5:25. This closes the third strophe or part of the prophecy under consideration. The fourth and last strophe occurs in Isaiah 10:1-4.