Quintilian, Institutio Oratoria, Book 11
Harold Edgeworth Butler, Ed.

[28] For such assertions may to some extent be justified by the age, rank, and authority of the speaker. But scarcely any orator is possessed of these advantages to such an extent as to exempt him from the duty of tempering such assertions by a certain show of modesty, a remark which also applies to all passages in which the advocate draws any of his arguments from his own person. What could have been more presumptuous than if Cicero had asserted that the fact that a man was the son of a Roman knight should never be regarded as a serious charge, in a case in which he was appearing for the defence? But he succeeded in giving this very argument a favourable turn by associating his own rank with that of the judges, and saying,¹ “The fact of a man being the son of a Roman knight should never have been put forward as a charge by the prosecution when these gentlemen were in the jury-box and I was appearing for the defendant.”