My Eyes Have Seen the King
Isaiah saw the Lord but he doesn't have the vocabulary to describe what he saw. The Lord's holiness is beautiful, the Seraphim sing about it. Isaiah can't join them because he knows his lips are unclean. Even the Seraphim cover their eyes. Sin separates us from God. At the moment he cries out, Isaiah is cleansed. By Christ's sacrifice there is hope.
The video of the entire service including recorded Hebron congregational singing can be viewed here.