Why was Isaiah pronouncing judgment on Israel?
The nation had fallen into sin and wickedness, turning from the Mosaic Law and the obedient system it once followed. Jerusalem, once a faithful city full of judgment and righteousness, had become a harlot filled with murderers. Isaiah therefore castigated Israel for its widespread corruption and departure from the Mosaic system.
Les explains that Isaiah is coming down on the nation of Israel because of all their sin and wickedness. In Isaiah chapter 1, verse 21, Isaiah asks how the faithful city has become a harlot. It had once been full of judgment and righteousness, but now it was full of murderers. Les identifies this as Jerusalem. At one time it had been a righteous city, and the Jewish people were obedient to the Mosaic Law and the system. But they had become so wicked that this city, once full of righteousness, was now full of murderers. That is why Isaiah is castigating the nation. The context also notes that Isaiah chapter 1, verse 22, contains the word translated corrupt in 2 Corinthians 2:17.