What does Isaiah 6:11 mean?
The words have been given by the Lord to Isaiah to preach to the people of Judah. They contain the promise of what appears to be a fruitless career for Isaiah. He will declare God's messages and warning about coming judgment, and the people will not understand it, accept it, or believe it. Isaiah's work will be to faithfully declare a truth to an unreceptive audience (Isaiah 6:9–10).Isaiah responds to the Lord's instruction now with one question: "How long?" Isaiah seems to be asking how long he should continue to carry out this futile work of declaring the Lord's truths to a people unable to receive them.
The answer from the Lord is equally hopeless, at least on the surface. He wants Isaiah to keep preaching His words to His unbelieving people until all is in ruin. This includes the cities, the people, the very land itself. In other words, God wants Isaiah to keep warning the people of the Lord's coming judgment on them for their sinfulness until that judgment is at hand. This will be Isaiah's entire career.