“Whom none could overcome with iron or gold.”
As quoted by Cicero in De Re Publica, Book III, Chapter IV
Iron is a metonym for sword/warfare, and gold for money/bribery.
Original
Quem nemo ferro potuit superare nec auro.
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Ennius 23
Roman writer -239–-169 BCRelated quotes

“Everything has its limit - iron ore cannot be educated into gold.”

“To have gold brings fear; to have none brings grief.”
English Proverbs (1659)

Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book VII, Chapter III, Sec. 5

“Not chaffering war but waging war, not with gold but with iron—thus let us of both sides make trial for our lives”
Nec cauponantes bellum sed belligerantes;
Ferro non auro vitam cernamus utrique.
As quoted by Cicero in De Officiis, Book I, Chapter XII

Source: The Self-Overcoming of Nihilism (1990), p. 180

(28th February 1824) Metrical Tales. Tale I. The Three Wells - A Fairy Tale
The London Literary Gazette, 1824