History of the Peloponnesian War

The Corinthians, in the presence of all the allies who, like themselves, had not acceded to the treaty, (for they had themselves previously invited them thither,) spoke in reply to the Lacedaemonians; not indeed directly stating the injuries they had received, namely, that they had not recovered Sollium from the Athenians, nor Anactorium—with any other point on which they considered themselves to be aggrieved; but urging as a pretext their determination not to betray the Thrace-ward Greeks; for they had taken oaths to them, both by themselves, when in the first instance they revolted, in concert with the Potidaeans, and others afterwards.

They were not then, they said, violating their oaths to the allies by refusing to accede to the treaty with the Athenians; for since they had sworn to their Thrace-ward friends, with appeals to the gods, they should not show a proper regard for their oaths, if they betrayed them. Besides, it had been expressly mentioned,

unless there were some impediment on the part of gods or heroes;