Verse 6
Shall a trumpet be blown - The sign of alarm and invasion.
And the people not be afraid? - Not take the alarm, and provide for their defense and safety?
Shall there be evil in a city - Shall there be any public calamity on the wicked, that is not an effect of my displeasure? The word does not mean moral evil, but punishment for sin; calamities falling on the workers of iniquity. Natural evil is the punishment of moral evil: God sends the former when the latter is persisted in.