According to Herodotus, when the Athenians and the Spartans killed some Persian messengers who had come demanding the submission of Greece to the will of the Persian king, divine punishment was the result.

To Athens and Sparta Xerxes [the Persian king] sent no demand for submission because of what happened to the messengers whom Darius had sent on a previous occasion at Athens they were thrown into the pit like criminals, at Sparta they were pushed into a well—and told that if they wanted earth and water for the king, to get them from there This time, therefore, Xerxes refrained from sending a request Just what disagreeable consequences were suffered by the Athenians for this treatment of the king's messengers, I am unable to say, perhaps it was the destruction of their city and the countryside around it&mdash...