Then I said: Woe is me, for I am ruined, because I am a man of unclean lips and live among a people of unclean lips, [and] because my eyes have seen the King, the Lord of Hosts.
Then one of the seraphim flew to me, and in his hand was a glowing coal that he had taken from the altar with tongs.
He touched my mouth [with it] and said: Now that this has touched your lips, your wickedness is removed, and your sin is atoned for.
Then I heard the voice of the Lord saying: Who should I send? Who will go for Us? I said: Here I am. Send me.
And He replied: Go! Say to these people: Keep listening, but do not understand; keep looking, but do not perceive.
Dull the minds of these people; deafen their ears and blind their eyes; otherwise they might see with their eyes and hear with their ears, understand with their minds, turn back, and be healed.
References for Isaiah 6:10
Then I said, "Until when, Lord?" And He replied: Until cities lie in ruins without inhabitants, houses are without people, the land is ruined and desolate,
and the Lord drives the people far away, leaving great emptiness in the land.
Though a tenth will remain in the land, it will be burned again. Like the terebinth or the oak, which leaves a stump when felled, the holy seed is the stump.