History of the Peloponnesian War
Thucydides
Thucydides. The history of the Peloponnesian War, Volume 1-2. Dale, Henry, translator. London: Heinemann and Henry G. Bohn, 1851-1852.
It was from this expedition that the first open quarrel arose between the Lacedaemonians and Athenians. For the Lacedaemonians, when the place was not taken by storm, fearing the boldness and innovating spirit of the Athenians—and moreover considering that they were of a different race from themselves—lest, if they remained, they might at the persuasion of those in Ithome attempt some revolution, dismissed them alone of all the allies; not letting their suspicion appear, but saying that they were no longer in any need of them.
The Athenians, however, knew that they were dismissed, not on the more creditable reason assigned, but from some suspicion having arisen: and considering it hard usage, and not thinking that they deserved to be so treated by the Lacedaemonians, immediately on their return they broke off the alliance which they had made with them against the Mede, and became allies of the Argives, their enemies. The same oaths also were taken, and the same alliance made by both with the Thessalians.
Those in Ithome, in the tenth year, when they could hold out no longer, surrendered to the Lacedaemonians on condition of their going out of the Peloponnese under truce, and never setting foot on it again;
and that if any one were caught doing so, he should be the slave of him who caught him. The Lacedaemonians had also before this a Pythian response made to them,
to let go the suppliant of Jupiter at Ithome.