History of the Peloponnesian War

But the rival factions of Megara were afraid, the one that he might bring in the exiles and drive them out, the other that the populace, fearing this very thing, might attack them, and that the city, being at war with itself, while the Athenians were lying in wait near at hand, might be ruined. They, therefore, did not admit Brasidas, both parties thinking it best to wait and see what would happen.

For each party expected that there would be a battle between the Athenians and the relieving army, and so it was safer for them not to join the side which anyone favoured until it was victorious. So then Brasidas, when he could not persuade them, withdrew once more to his own army.