Do not shun this maxim because it is common-place. On the contrary, take the closest heed of what observant men, who would probably like to show originality, are yet constrained to repeat. Therein lies the marrow of the wisdom of the world. – Arthur Helps, “Chapter IV,” Companions of My Solitude, 1851

And in spite of his practical ability, some of his experience had petrified into maxims and quotations. – George Eliot (Mary Ann Evans), Daniel Deronda (Book II, Meeting Streams), 1876

Not everything that can be extracted appears in anthologies of quotations, in commonplace books, or on the back of Celestial Seasonings boxes. Only certain sorts of extracts become quotations. – Gary Saul Morson, The Words of Others: From Quotations to Culture, 2011

I wonder if “an” ever occurs before “haughty” except in a quotation, or whether you can make anything sound like a quotation by adding a word like “goeth”? – Gary Saul Morson, The Words of Others: From Quotations to Culture, 2011