I am new... I am not sure if I should be asking this here or not. Please advise if I should do something else.

Here is the question: In Is. 6 God sent Isaiah to preach repentance. So why did God tell Isaiah to do that and simultaneously harden the hearts of the hearers (V.9-10)?

Thank you

This doesn't make sense if you are imagining that God is imposing hard hearts onto His beloved children against their will. He is not doing that. He is saying what He sees: He sees them hearing but not understanding and seeing but not perceiving because their hearts are against Him even if their words and actions appear okay. Isaiah is being sent to tell the people that God can see what is really going on.