“Well-timed silence hath more eloquence than speech.”
Martin Fraquhar Tupper

"There is not only an art, but an eloquence in it." 
Marcus Tullius Cicero 

“Silence is argument carried out by other means.”
Ernesto ‘Che’ Guevara

“If a word is worth a coin, silence is worth two.”
Hebrew Proverb 

“The ideal man is his own best friend and takes delight in privacy.”
Aristotle 

“A quiet mind cureth all.”
Robert Burton 

“I think the first virtue is to restrain the tongue: he approaches nearest to the Gods, who knows how to be silent, even though he is in the right.”
Cato 

“In silence man can most readily preserve his integrity.” 
Meister Eckhart 

“He that would live in peace and at ease, must not speak all he knows, nor judge all he sees.”
Benjamin Franklin 

In the End, we will remember not the words of our enemies, but the silence of our friends.
Martin Luther King, Jr.

Silence is a true friend who never betrays.
Confucius

He who does not understand your silence will probably not understand your words.
Elbert Hubbard

Silence is one of the hardest arguments to refute.
Josh Billings

Nothing strengthens authority so much as silence.
Leonardo da Vinci