History of the Peloponnesian War

For at present the commons in all the states are well disposed towards you, and either do not revolt with the aristocratical party, or if compelled to do so, are straightway hostile to those who made them; and you have the mass of the city opposed to you on your side, when you proceed to war.

But if you butcher the commons of Mytilene, who took no part in the revolt, and when they had got possession of arms, voluntarily gave up the city; in the first place you will act unjustly by slaying your benefactors; and in the next you will produce for the higher classes of men a result which they most desire; for when they lead their cities to revolt, they will immediately have the commons on their side, because you had shown them beforehand that the same penalty is appointed for those who are guilty and those who are not.