Quintilian, and J.S. Watson. Institutes of Oratory. Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book 12 Chapter 3.
In book 12 chapter 3 Quintilian reminds the reader that an orator must be familiar with law, customs, and religion of a state in order to exercise influence. Without such wide ranging understanding he cannot convince a judge of a policy (Quintilian XII.3.2). Great familiarity is needed especially for dealing with cross examinations (Quintilian XII.3.3). Knowledge of customs and laws should be an easy thing. All can be learned by observation and research (Quintilian XII.3.7). A sensible orator should therefore be well prepared for cases. Quintilian wholeheartedly endorses the idea of reading extensively. This is the orator’s most necessary habit.