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.
For if they had not shown themselves there, they would not have had a chance, but would certainly have lost the city, being considered as good as beaten. But as it was, the Athenians might happen to be not disposed for a contest; so that without fighting they would succeed in the objects of their coming. And this was indeed the case.
For the Athenians came out, and drew up by the long walls, but remained quiet on their side also, as the enemy did not attack them: since their commanders too considered it no equal hazard, on the one hand for them, after succeeding in most of their designs, to commence an engagement against superior numbers, and either, if victorious, only to take Megara, or, if beaten, to sacrifice the flower of their heavy-soldiery; and, on the other hand, for merely a part of their enemies' whole force, nay even of that which was present in each case, to be willing, as they reasonably might, with boldness to risk a battle. So when, after waiting some time and no attack being made on either side, the Athenians first returned to Nisaea, and then the Peloponnesians to the point they had set out from; under these circumstances the friends of the Megarean exiles with greater confidence threw open the gates to Brasidas and the commanders from the different states, (considering that he had proved his superior strength, and that the Athenians had no longer been willing to fight,) and having received them, proceeded to confer with them, while those who had negotiated with the Athenians were now confounded.
Afterwards, when Brasidas had dismissed the allies to their several cities, he himself went back to Corinth, and prepared for his expedition to Thrace, which was his original destination.
When the Athenians also had returned home, such of the Megareans in the city as had been most implicated in the negotiations with them, knowing that they had been marked, immediately stole away; while the rest, having conferred with the friends of the exiles, restored the party at Pegae, after binding them by solemn oaths to forget the past, and to advise what was best for the city.