Isaiah 6:5-7

5And I said, Woe unto me! for I am undone; for I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for mine eyes have seen the King, Jehovah of hosts.

6And one of the seraphim flew unto me, and he had in his hand a glowing coal, which he had taken with the tongs from off the altar;

7and he made it touch my mouth, and said, Behold, this hath touched thy lips; and thine iniquity is taken away, and thy sin expiated.