Isaiah confesses he is unclean and living among an unclean people after seeing the King (Isaiah 6:5). A seraph touches his mouth with a burning coal from the altar and declares his guilt taken away and sin atoned for (Isaiah 6:6-7).
In Isaiah 6:5–7, Isaiah responds to the vision of Yahweh with shock and self-condemnation, saying he is ruined because his speech is unclean and he lives among a people like him. A seraph brings a burning coal from the altar, touches Isaiah’s mouth, and announces that the touch has removed Isaiah’s guilt and dealt with his wrongdoing. These verses sit inside Isaiah’s call vision in chapter 6, where the prophet sees Yahweh enthroned and hears the seraphim’s repeated cry of holiness (6:1–4).
Isaiah’s reaction is a crisis of exposure: he sees “the King, Yahweh of Hosts,” and immediately speaks a “woe” over himself (explicit in verse 5). He names the problem as “unclean lips,” and he includes his community in the diagnosis (“a people of unclean lips”). The text ties his fear directly to being in the presence of the holy King.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Isaiah 6:5, then read the surrounding section so the answer stays connected to the passage's flow.
5Then said I, Woe is me! for I am undone; because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips: for my eyes have seen the King, Yahweh of Hosts.