“Courage originally meant "To speak one's mind by telling all one's heart.”

Variant: Science tells me God must exist.
My mind tells me I'll never understand God.
My heart tells me I'm not meant to.

[Vittoria Vetra]
Source: Angels & Demons

The Republic Gives Thanks (2018)

"Lettre XII: sur M. Pope et quelques autres poètes fameux," Lettres philosophiques (1756 edition)
Variants:
He looked on everything as imitation. The most original writers, he said, borrowed one from another. Boyardo has imitated Pulci, and Ariofio Boyardo. The instruction we find in books is like fire; we fetch it from our neighbour, kindle it as home, communicate it to others, and it becomes the property of all.
Historical and Critical Memoirs of the Life and Writings of M. de Voltaire (1786) by Louis Mayeul Chaudon, p. 348
What we find in books is like the fire in our hearths. We fetch it from our neighbors, we kindle it at home, we communicate it to others, and it becomes the property of all.
As translated in Geary's Guide to the World's Great Aphorists (2008), by James Geary, p. 373
Context: Thus, almost everything is imitation. The idea of The Persian Letters was taken from The Turkish Spy. Boiardo imitated Pulci, Ariosto imitated Boiardo. The most original minds borrowed from one another. Miguel de Cervantes makes his Don Quixote a fool; but pray is Orlando any other? It would puzzle one to decide whether knight errantry has been made more ridiculous by the grotesque painting of Cervantes, than by the luxuriant imagination of Ariosto. Metastasio has taken the greatest part of his operas from our French tragedies. Several English writers have copied us without saying one word of the matter. It is with books as with the fire in our hearths; we go to a neighbor to get the embers and light it when we return home, pass it on to others, and it belongs to everyone

God doesn't believe in atheists (2002)

Source: Aphorisms and Reflections (1901), p. 234