Charles Ellicott Commentary Isaiah 54:15

"Behold, they may gather together, but not by me: whosoever shall gather together against thee shall fall because of thee." — Isaiah 54:15 (ASV)

But not by me ... —Another contrast with Isaiah’s experience. The power of Sargon and Sennacherib rested on the fact that they were instruments in God’s hands (Isaiah 10:15; Isaiah 37:26). Against the new Jerusalem no command would be given such as had been given to them.