What was Jerusalem like before it became wicked in Isaiah 1?
Before its wickedness, Jerusalem was the faithful city, full of judgment and righteousness; righteousness lodged in it. Its people were obedient to the Mosaic Law and its system. Isaiah contrasts that former righteous condition with its later state as a harlot and full of murderers.
Les explains from Isaiah 1:21-22 that Isaiah was coming down on the nation of Israel because of all their sin and wickedness. The city in view is 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 the city once full of righteousness was now full of murderers. In verse 22, the same passage connects to the word translated corrupt in 2 Corinthians 2:17.
How is the faithful city become an harlot! it was full of judgment; righteousness lodged in it; but now murderers.