Question: The phrase "Man will believe anything, as long as it's not in the Bible" is attributed to Napoleon on many sites but there are no further details (date, context,etc.) available, nor a trace of primary sources.

Some examples:
[AZ Quotes](https://www.azquotes.com/quote/1056429), [Quote Fancy](https://quotefancy.com/quote/870652/Napoleon-Man-will-believe-anything-as-long-as-it-s-not-in-the-bible), [Love Expands](https://loveexpands.com/quotes/napoleon-bonaparte-700294/).

Answer: 
To a bit more history here, there's a 1998 book
*Soaring and Settling* by [Rita Gross](https://en.wikipedia.org/wiki/Rita_Gross), which has a different take/version (p. 43):

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> I am just as frustrated that many Caucasian Buddhists, reasonably sophisticated in their assessments of certain elements of Christian tradition that are woefully out of date, will believe anything as long as it is said by a Tibetan lama.
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I suspect it's this passage or something similar that was the basis of the post-2000 broader but similar pronouncements.

Regarding Napoleon, he [generally](https://journals.openedition.org/rh19/622) found Catholicism useful, but Protestantism not so much. So it's quite unlikely he would have said something that simplistic about the Bible. On the other hand, Napoleon was/is more often demonized or derided in Protestant circles, which is a more plausible reason why the quote might have been attributed to him in such circles.
There have been similar phrases uttered by many different people. Very often, it is said by religious leaders attacking atheism, especially by creationists attacking Darwinism.

Attribution to Napoleon goes back a long way. [Here's a book from 1883](https://www.google.co.uk/books/edition/The_Church_Review/pAPOAAAAMAAJ?hl=en&gbpv=1&dq=Duroc%20%22believe%20anything%22&pg=PA14&printsec=frontcover). Note that the anecdote is uncited, and told by an anti-Darwinist. Very probably apocryphal.

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> It is related of Napoleon that one day his friend Duroc was reciting to him a marvelous story. Duroc was a skeptic, indeed more than that - an avowed unbeliever. As he ended the improbable tale Napoleon answered "Some men can believe anything but the Bible."
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[Here's an earlier example](https://www.google.co.uk/books/edition/Life/mNwXAAAAYAAJ?hl=en&gbpv=1&dq=%22believe%20anything%22%20%22not%20in%20the%20bible%22&pg=PA81&printsec=frontcover),from 1868, attributing the remark to Napoleon speaking of Duroc, without context, and without a cite.

The [earliest example](https://www.google.co.uk/books/edition/British_and_Foreign_Medico_chirurgical_R/205YAAAAMAAJ?hl=en&gbpv=1&dq=%22believe%20anything%22%20%22not%20in%20the%20bible%22&pg=PA173&printsec=frontcover) I've been able to find of the phrase itself is in a medical journal dated July 1852. No attribution to Napoleon.

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> It is an old observation that complete scepticism in religion is often allied with extraordinary credulity in other matters; and we have a remarkable verification of this in the present time, in the authors of 'Man's Nature and Development' of one of whom it has been not unaptly or untruly remarked, that "she will believe anything that is not in the Bible."
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