“Persuasion hung upon his lips, and the elements of Logick and Rhetorick were so blended up in him, — and, withall, he had so shrewd guess at the weaknesses and passions of his respondent, — that NATURE might have stood up and said, — "This man is eloquent."”

my father gained half in half, and consequently was as well again off, as if it had never befallen him.
Book V, Ch. 3.
The Life and Opinions of Tristram Shandy, Gentleman (1760-1767)

Les passions sont les seuls orateurs qui persuadent toujours. Elles sont comme un art de la nature dont les règles sont infaillibles; et l'homme le plus simple qui a de la passion persuade mieux que le plus éloquent qui n'en a point.
Variant translation: The passions are the only orators who always persuade. They are like a natural art, of which the rules are unfailing; and the simplest man who has passion will be more persuasive than the most eloquent man who has none.
Maxim 8.
Reflections; or Sentences and Moral Maxims (1665–1678)

Source: Lover Mine

From Here to Eternity (1951)

On Kippis; Gregory’s Life of Hall, reported in Bartlett's Familiar Quotations, 10th ed. (1919).

Source: The Alexandria Quartet (1957–1960), Mountolive (1958), VIII

1810s, Letter to William Tudor (1818)

Source: Darkfever

The Decline and Fall of Practically Everybody (1950), Part II: Ancient Greeks and Worse, Hannibal