In that day shall there be a great mourning in Jerusalem, as the mourning of Hadadrimmon in the valley of Megiddon. A great mourning - A universal repentance.
As the mourning of Hadadrimmon - They shall mourn as deeply for the crucified Christ as their forefathers did for the death of Josiah, who was slain at Hadadrimmon in the valley of Megiddon. See 2 Chronicles 35:24, 2 Chronicles 35:25.