Isaiah 6:5-8

And I said: "Woe to me! For I have remained silent. For I am a man of unclean lips, and I live in the midst of a people having unclean lips, and I have seen with my eyes the King, the Lord of hosts!" And one of the Seraphims flew to me, and in his hand was a burning coal, which he had taken with tongs from the altar. And he touched my mouth, and he said, "Behold, this has touched your lips, and so your iniquities will be taken away, and your sin will be cleansed." And I heard the voice of the Lord, saying: "Whom shall I send?" and, "Who will go for us?" And I said: "Here I am. Send me."