Quintilian, Institutio Oratoria, Vol. IV (Loeb)

20 For a long time we should read none save the best authors—those least likely to deceive the one who trusts them—and we should do so diligently, with almost the same care as if we were writing it ourselves. We must not examine everything merely in parts; a book, once read, must be taken up again in its entirety, especially speeches, the virtues of which are often deliberately hidden. 21 For the orator often prepares, dissembles, and sets a trap, saying things in the first part of a speech that will prove most useful in the conclusion. Therefore, they seem less effective in their own place because we do not yet know why they were said; thus, once everything is understood, they must be re-read. 22 It is most useful to know the facts of the cases whose speeches we have taken in hand, and, whenever possible, to read the speeches delivered on both sides: such as those of Demosthenes and Aeschines against one another, or Servius Sulpicius and Messala—one of whom spoke for Aufidia, the other against her—or those of Pollio and Cassius in the case of Asprenas, and many others. 23 Indeed, even if some seem less equal in merit, they will still be rightly sought out for understanding the questions of the legal cases, such as the speeches of Tubero against Ligarius compared with Cicero’s, or Hortensius in the defense of Verres compared with the counter-argument. It will also be useful to know how different people pleaded the same case.