The public is a ferocious beast: one must chain it up or flee from it.
Le public est une bête féroce: il faut l'enchaîner ou la fuir.
Original text (French)
Notes from Wikiquote
Letter to Mademoiselle Quinault, quoted in Charles Sainte-Beuve, "Lettres inédites de Voltaire," Causeries de Lundi (20 October 1856) ; an English translation can be found on this page