Isaiah 6:5-7

5So I said: “Woe is me, for I am undone! Because I am a man of unclean lips, And I dwell in the midst of a people of unclean lips; For my eyes have seen the King, The Lord of hosts.”

6Then one of the seraphim flew to me, having in his hand a live coal which he had taken with the tongs from the altar.

7And he touched my mouth with it, and said: “Behold, this has touched your lips; Your iniquity is taken away, And your sin purged.”