What does Isaiah 6:9 mean?
Isaiah has eagerly volunteered to go and represent God's message to the people of Judah (Isaiah 6:8). Now the Lord begins to reveal to Isaiah what shape this message will take. It is not the hopeful one.His first message to the people of Judah would be to tell them not to listen to him. The purpose here is not that God explicitly, forcibly stops people from understanding or repenting. Prophets were sometimes told to deliver messages as if they, themselves, were accomplishing some task (Jeremiah 1:10) He is stating that God's words, through Isaiah, will fall on closed ears. Isaiah was commanded to deliver a message from God but warned that he should not expect them to receive it.
This and the following verse (Isaiah 6:10) show that God knows the people of Judah are already too far gone into their sin to turn back before judgment comes. Still, the Lord will be faithful to tell them the truth, even if He will not help them to act on it. Maybe more importantly, the Lord will be faithful to future generations through Isaiah's messages. They will hear, through Isaiah's writings, both the Lord's call to Judah to repent and the price paid by Judah for refusing to repent.