Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
III. In the natural order of things the statement of fact is followed by the verification. For it
This practice originated in the display of the schools of declaration and thence extended to the courts as soon as causes came to be pleaded, not for the benefit of the parties concerned, but to enable the advocates to flaunt their talents. I imagine that they feared that if the slender stream of concise statement, such as is generally required, were followed by the pugnacious tone inevitable in the arguing of the case, the speech would fall flat owing to the postponement of the pleasures of a more expansive eloquence.