Thucydides, History of the Peloponnesian War
Benjamin Jowett, Ed.

43. When the difference between the Lacedaemonians and Athenians had gone thus far, the war¹ party at Athens in their turn lost no time in pressing their views. [2] Foremost among them was Alcibiades the son of Cleinias, a man who would have been thought young in any other city, but was influential by reason of his high descent: he sincerely preferred the Argive alliance, but at the same time he took part against the Lacedaemonians from temper, and because his pride was touched. For they had not consulted him, but had negotiated the peace through Nicias and Laches, despising his youth, and disregarding an ancient connexion with his family, who had been their proxeni; a connexion which his grandfather had renounced, and he, by the attention which he had paid to the captives from Sphacteria, had hoped to have renewed. Piqued at the small respect which was shown to all his claims, he had originally opposed the negotiations; [3] declaring that the Lacedaemonians were not to be trusted, and that their only object in making terms was that they might by Athenian help crush the Argives, and afterwards attack the Athenians themselves when they had no friends. As soon as the rupture occurred he promptly despatched a private message to the Argives, bidding them send an embassy as quickly as they could, together with representatives of Mantinea and Elis, and invite the Athenians to enter the alliance; now was the time, and he would do his utmost to assist them.