“An error does not become truth by reason of multiplied propagation, nor does truth become error because nobody sees it. Truth stands, even if there be no public support. It is self sustained.”

Also translated as: Truth does not need to borrow garments from falsehood.
Noli me Tangere

The Tragic Sense of Life (1913), V : The Rationalist Dissolution

Source: The Guide for the Perplexed

Introductio ad prudentiam: Part II (1727), Gnomologia (1732)

Es ist so gewiß als wunderbar, daß Wahrheit und Irrthum aus Einer Quelle entstehen; deßwegen man oft dem Irrthum nicht schaden darf, weil man zugleich der Wahrheit schadet.
Maxims and Reflections (1833)

Heaven Taken By Storm

"Religion: A Dialogue."
Variant translation: To free a man from error does not mean to take something from him, but to give him something.
Essays
Source: Essays and Aphorisms
Context: To free a man from error is to give, not to take away. Knowledge that a thing is false is a truth. Error always does harm; sooner or later it will bring mischief to the man who harbors it. Then give up deceiving people; confess ignorance of what you don't know, and leave everyone to form his own articles of faith for himself. Perhaps they won't turn out so bad, especially as they'll rub one another's corners down, and mutually rectify mistakes. The existence of many views will at any rate lay a foundation of tolerance. Those who possess knowledge and capacity may betake themselves to the study of philosophy, or even in their own persons carry the history of philosophy a step further.