Charles Ellicott Commentary Isaiah 28:21

"For Jehovah will rise up as in mount Perazim, he will be wroth as in the valley of Gibeon; that he may do his work, his strange work, and bring to pass his act, his strange act." — Isaiah 28:21 (ASV)

The Lord shall rise up as in mount Perazim ... — The point of the reference to David’s victories at Baal Perazim (2 Samuel 5:20; 1 Chronicles 14:11), and at Gibeon (1 Chronicles 14:16) is that then Jehuah had interposed on behalf of His people against their enemies. The “new and strange” work—the very paradox of prophecy—was that He would now rise up to overthrow His own people.