Full Idea
If we take in hand any volume of divinity or metaphysics, ask 'Does it contain any abstract reasoning concerning quantity or number?' No. 'Or experimental reason on matters of fact and existence?' No. Commit it then to the flames.
Gist of Idea
If books don't relate ideas or explain facts, commit them to the flames
Source
David Hume (Enquiry Conc Human Understanding [1748], XII.III.132)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.165