Isaiah 6:1-8 (ESV)

 In the year that King Uzziah died I saw the Lord sitting upon a throne, high and lifted up; and the train of his robe filled the temple. Above him stood the seraphim. Each had six wings: with two he covered his face, and with two he covered his feet, and with two he flew. And one called to another and said:

  “Holy, holy, holy is the LORD of hosts;
  the whole earth is full of his glory!”

And the foundations of the thresholds shook at the voice of him who called, and the house was filled with smoke. And I said: “Woe is me! For I am lost; for 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!”

Then one of the seraphim flew to me, having in his hand a burning coal that he had taken with tongs from the altar. And he touched my mouth and said: “Behold, this has touched your lips; your guilt is taken away, and your sin atoned for.”

And I heard the voice of the Lord saying, “Whom shall I send, and who will go for us?” Then I said, “Here I am! Send me.”