History of the Peloponnesian War

At the end of the same summer, Aristeus, a Corinthian, Aneristus, Nicolaus, and Stratodemus, ambassadors of the Lacedaemonians, Timagoras, a Tegean, and Pollis, an Argive in a private capacity, being on their way to Asia, to obtain an interview with the king, if by any means they might prevail on him to supply money and join in the war, went first to Thrace, to Sitalces the son of Teres, wishing to persuade him, if they could, to withdraw from his alliance with the Athenians, and make an expedition against Potidaea, where was an armament of the Athenians besieging the place; and then, to proceed by his assistance to their destination across the Hellespont, to Pharnaces the son of Pharnabazus, who was to send them up the country to the king.

But some Athenian ambassadors, Learchus son of Callimachus, and Aminiades son of Philemon, happening to be with Sitalces, persuaded Sadocus his son, who had been made an Athenian citizen, to put the men into their hands, that they might not, by passing over to the king, do their best to injure [what was now] his own country.

He, in compliance with their request, having sent some other men with Learchus and Aminiades, seized them as they were travelling through Thrace to the vessel in which they were to cross the Hellespont, before they went on board, and gave orders to deliver them up to the Athenian ambassadors;

who, having received them, took them to Athens. On their arrival the Athenians, being afraid that if Aristeus escaped he might do them still more mischief, (for even before this he had evidently conducted all the measures in Potidaea and their possessions Thrace-ward,) without giving them a trial, though they requested to say something [in their own defence], put them to death that same day, and threw them into pits; thinking it but just to requite them in the same way as the Lacedaemonians had begun with; for they had killed and thrown into pits the merchants, both of the Athenians and their allies, whom they had taken on board trading vessels about the coast of the Peloponnese. Indeed all that the Lacedaemonians took on the sea at the beginning of the war, they butchered as enemies, both those who were confederates of the Athenians and those who were neutral.