What does Isaiah 9:18 mean?
Isaiah continues to deliver a prediction of God's judgment on the wicked people of that era. This chapter concludes with four verses (Isaiah 9:19–21) describing the nature of Israel's sinfulness. It is not simply that they have neglected to worship the Lord and seek help from Him. The people of Israel have been leading self-serving, wicked lifestyles.Scripture uses the metaphor of wildfire to depict the spread of wickedness. It consumes the briers and thorns along the ground first. Gaining momentum, it finds more fuel in the thickets and then begins to ignite the trees themselves. Soon a huge column of smoke can be seen towering over the forest.
Sinfulness, too, begins with smaller rebellions, simple and easy disobedience. The appetite for sin grows and more fuel is needed to get the same level of rush. New sins are explored. Sinful habits become sinful lifestyles. Sinful lifestyles are shared and turn into sinful neighborhoods and communities. This had happened in Israel, and the time of the Lord's judgment for sin had come.