Isaiah 6:5 - Matthew Poole's English Annotations on the Holy Bible

I am a man of unclean lips; I am a great sinner, as many other ways, so particularly by my lips, which being in a special manner consecrated to God by my prophetical office, should have been entirely devoted to him; but, alas! my speeches, either to God in prayer, or from God in preaching and prophesying to the people, have been mixed and defiled with so much irreverence, dulness, distraction of thoughts and affections, carnal fear, and many other infirmities, that I dread the thoughts of appearing before thy judgment-seat, which I see erected in this place. For Isaiah had been a prophet before this time, Isaiah 1:1, and was now called, not in general to his prophetical office, but to the delivery of this special message. I dwell in the midst of a people of unclean lips; I am an unclean branch of an unclean tree; and besides my own uncleanness, I have both by my omissions and commissions involved myself in the guilt of their sins, and therefore may justly fear to partake with them in their plagues. Mine eyes have seen the King, the Lord of hosts; the sight of this glorious and holy God gives me cause to fear that he is come to judgment against me, together with others. Whilst sinners are secure and presumptuous, the holiest persons have ever been filled with great reverence, and ofttimes with doubts and fears, at any extraordinary manifestation of God's presence. See Genesis 16:13, Genesis 17:3 Judges 13:22.