There was a gourmand so greedy that he left nothing for his table companions. A large fish having been served, Zeno took it up as if he were about to eat the whole. When the other looked at him, “What do you suppose,” said he, “those who live with you feel every day, if you cannot put up with my gourmandise in this single instance?” A youth was putting a question with more curiosity than became his years, whereupon Zeno led him to a mirror, and bade him look in it; after which he inquired if he thought it became anyone who looked like that to ask such questions. Some one said that he did not in general agree with Antisthenes, whereupon Zeno produced that author's essay on Sophocles, and asked him if he thought it had any excellence; to which the reply was that he did not know. “Then are you not ashamed,” quoth he, “to pick out and mention anything wrong said by Antisthenes, while you suppress his good things without giving them a thought?”
Source: Dio Chrysostom Volume I-V. Loeb Classical Library. Discourses. Translated by J. W. Cohoon and H. Lamar Crosby. 1940.