Plutarch, Quomodo adulator ab amico internoscatur
Goodwin, Ed.

Well then, you say, when is a keen reprehension allowable, and when may we chide a friend severely indeed? I answer, when some important occasion requires it, as the stopping him in the career of his voluptuousness, anger, or insolence, the repressing his covetous humor or [p. 146] any other foolish habit. Thus dealt Solon with Croesus, puffed up and debauched with the uncertain greatness of his fortune, when he bade him look to the end. Thus Socrates humbled Alcibiades, forced him into unfeigned tears, and turned his heart, when he argued the case with him. Such, again, were the remonstrances and admonitions of Cyrus to Cyaxares, and of Plato to Dion, who, when the lustre and greatness of his achievements had fixed all men's eyes upon him, wished him to beware of arrogance and self-concept, as the readiest way to make all men abandon him. And Speusippus wrote to him, not to pride himself in the little applauses of women and children, but to take care to adorn Sicily with religion, justice, and wholesome laws, that he might render the Academy great and illustrious. So did not Euctus and Eulaeus, two of Perseus's favorites; who fawned upon and complied with him as obsequiously as any courtier of them all during the success of his arms, but after his defeat at Pydna by the Romans inveighed bitterly against him, reminding him of his past faults, till the man out of mere anger and vexation stabbed them both on the spot. And so much concerning the timing our reproofs in general.