Histories

Having spoken in this way, Xerxes passed over the place where the dead lay and hearing that Leonidas had been king and general of the Lacedaemonians, he gave orders to cut off his head and impale it.

It is plain to me by this piece of evidence among many others, that while Leonidas lived, king Xerxes was more incensed against him than against all others; otherwise he would never have dealt so outrageously with his dead body, for the Persians are beyond all men known in the habit of honoring valiant warriors. They, then, who received these orders did as I have said.