This kind of rebuking is also called a pleading with them; so he threatens to plead against Gog with pestilence and blood, Eze_38:22. God at first pleads with sinners by words; but if he cannot so prevail, he will plead with them in a way by which he will overcome by fire, pestilence, and blood.
With all flesh; thus he threatens to do with all sinners, or with all the wicked Jews.
The slain of the Lord shall be many; to the fire he threatens to add the sword, so as the slain of the Lord, that is, those whom God should cause to be slain, should be many.