De Somniis (lib. i-ii)

And by these means nature prepares and trains man for both objects, speech and silence, watching the appropriate time for each employment. As for instance, is anything said worth listening to? Then attend, raising no obstacle, in perfect quiet, according to the injunction of Moses, "Be silent and hear." [*](Deut. xxvii. 19. )

For of those persons who mix themselves up in contentious discussions there is not one who can properly be considered as either speaking or listening; but this is only advantageous to him who is about to do so.