Isaiah 6:1-7
6 In the year that King Uzziah died I saw the Lord sitting upon a throne, high and lifted up; and the train[a] of his robe filled the temple. 2 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. 3 And one called to another and said:
“Holy, holy, holy is the Lord of hosts;
the whole earth is full of his glory!”[b]
4 And the foundations of the thresholds shook at the voice of him who called, and the house was filled with smoke. 5 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!”
6 Then one of the seraphim flew to me, having in his hand a burning coal that he had taken with tongs from the altar. 7 And he touched my mouth and said: “Behold, this has touched your lips; your guilt is taken away, and your sin atoned for.” (ESV)