Isaiah 6:3-7

And one called out to another and said, “Holy, Holy, Holy, is the Lord of armies. The whole earth is full of His glory.”

And the foundations of the thresholds trembled at the voice of him who called out, while the temple was filling with smoke.

Then I said, “Woe to me, for I am ruined! Because I am a man of unclean lips, And I live among a people of unclean lips; For my eyes have seen the King, the Lord of armies.”

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

He touched my mouth with it and said, “Behold, this has touched your lips; and your guilt is taken away and atonement is made for your sin.” Isaiah’s Commission