History of the Peloponnesian War

Now when Phrynichus had discovered beforehand that he was doing him injury, and that a letter from Alcibiades on the subject was on the point of arriving, he himself anticipated it by announcing to the army, that as Samos was unfortified, and all the ships were not stationed within the harbour, the enemy intended to attack the camp: that he had certain intelligence of this, and that they ought as quickly as possible to fortify Samos and put every thing else in a state of defence. Now he was himself general, and so had full authority to carry out these measures. Accordingly they prepared for the work of fortification;

and owing to this Samos was the more quickly walled, though it would have been so under any circumstances. Not long after came the letters from Alcibiades, saying that the army was going to be betrayed by Phrynichus, and that the enemy were on the point of attacking them.

As, however, Alcibiades was not thought to be worthy of credit, but to have had a previous acquaintance with the plans of the enemy, and through personal dislike to have attributed them to Phrynichus, as though he were privy to them, he did him no harm, but rather bore witness to his statement by sending this intelligence.