Then said I, 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.
All Commentaries on Isaiah 6:5 Go To Isaiah 6
Cassiodorus Senator
AD 585
By “mouth” [or lips] is meant the hidden region of the heart, from which God’s praise is efficaciously sung. So he rightly proclaims after the forgiveness of his sin that his lips will be opened and that his mouth can announce the praise of the Lord.