Plataicus (25-27)

and they assert that it is to the advantage of their allies that the Thebans should have our country—fools that they are, not to know that no advantage ever accrues to those who unjustly seek greedy gain; on the contrary, many a people that have unjustly coveted the territory of others have with justice brought into the greatest jeopardy their own.

But one thing the Thebans will not be able to say—that they remain loyal to their associates, though there is reason to fear that we, having recovered our country, will desert to the Lacedaemonians; for you will find, Athenians, that we have twice been besieged[*] and forced to surrender because of our friendship for you, while the Thebans often have wronged this city.

It would be a laborious task to recount their treacheries in the past, but when the Corinthian war broke out because of their overbearing conduct and the Lacedaemonians had marched against them, although the Thebans had been saved by you, they were so far from showing their gratitude for this service that, when you had put an end to the war, they abandoned you and entered into the alliance with the Lacedaemonians.