"God is in the midst of her; she shall not be moved."
1. The circumstances of the declaration. 2. The certainty of the declaration. 3. The security of the declaration.
Please note that toward the end of this sermon, commenting on Isaiah 37.36, the preacher suggested that God sent 'one single angel' to slay Sennacherib's troops, and then asked how much more comfort we might expect from the presence of God himself.
He subsequently suggested what he considers a more plausible interpretation, which is that God himself - the Angel of the Lord, the pre-incarnate Christ - did indeed come forth for his people. This further emphasises the point being made, and drives home the comfort and security of God's people, albeit in a slightly different way.