What was Jerusalem like before the judgment described in Isaiah 1?

Before the judgment, Jerusalem was a faithful city, full of judgment and righteousness; righteousness lodged in it. The Jewish people were obedient to the Mosaic Law and its system. Isaiah contrasts this former righteous condition with its later state as a harlot and full of murderers.

Les explains that Isaiah is coming down on the nation of Israel because of their sin and wickedness, and he identifies the city in view as Jerusalem. In Isaiah 1:21, the faithful city is described as having been full of judgment, with righteousness lodged in it, but now it has become a harlot and is full of murderers. Les points out that Jerusalem had at one time been a righteous city, and the Jewish people were obedient to the Mosaic Law and the system. Their wickedness changed that condition.

Isaiah 1:21

How is the faithful city become an harlot! it was full of judgment; righteousness lodged in it; but now murderers.

What city is Isaiah 1:21 talking about when it says the faithful city became a harlot?

Isaiah 1:21 refers to Jerusalem. The faithful city that became a harlot is Jerusalem, which had once been full of judgment and righteousness but had turned to murderers and wickedness. This is the city the prophet Isaiah was addressing when he rebuked the nation of Israel for its sin.