The prophet Isaiah had a crisis encounter with God in Isaiah 6 that defined his calling. When Isaiah encountered God's holiness and presence, he cried out, “I'm doomed. I have filthy lips.” Isaiah got a revelation of his own sin in God's presence.
“Woe to me!” I cried. “I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the Lord Almighty.” Isaiah 6:5