(Isa. 6:5) Why does Isaiah emphasize his unclean lips?

CLAIM: Isaiah specifically says that he has “unclean lips” (Isa. 6:5). Why does he emphasize his lips and not some other feature on his body?

RESPONSE: Isaiah probably emphasizes his “lips,” because he is going to become a prophet. How can you speak for God, if you have unclean lips? This is the same God whose voice makes the foundations tremble (v.4). In addition, this could be an example of Jesus’ statement: “For his mouth speaks from that which fills the heart” (Lk. 6:45). Therefore, Isaiah could be claiming that he knows his heart is unclean, because his lips bear testimony to this.