What does Isaiah 9:20 mean?
The destructive power of sin is a terrible force. Isaiah has used fire as a metaphor to show how godlessness and immorality spread and grow in power. That trend eventually burns everything in its path and leads to more burning in the form of God's wrath (Isaiah 9:18–19). Now Isaiah, subtly changes metaphors to describes sin as a way of devouring other people. A few commentators suggest this is a reference to actual cannibalism in Israel. In this interpretation, this could have been the result of enemy sieges cutting off food supplies. More likely, though, Isaiah is describing the appetite for sin.Sin is never satisfied. Even when it destroys others. The more the appetite is fed, the more it grows, like a fire burning out of control (James 3:5; Psalm 83:14). We destroy ourselves and everyone within reach to feed our want for wickedness. This endless, unchecked feast of evil is why God's destruction was coming on Israel.