Isaiah realized that in this place of holiness, filled with the pristine righteousness and holiness of God - he was unclean, filthy and defiled as he stood in the presence of the most high God. Isaiah was accutely aware that God could not tolerate his filthiness. He know he was ruined, destined to be cast out of God's presence forever. One of God's seraphs flew to Isaiah with a live coal form the altar. He touched Isaiah's lips with it, transforming him. He was made clean and pure, totally acceptable to our most Holy God. The burniong coal symbolizes those things which we have confessed to God in prayer. This was a turning point for Isaiah. Now completely dedicated to God, Isaiah responds by completely giving himself to the will of God.
We never realize how filthy and unclean we are until we are in the presence of God.
