The ancients, who in these matters were not perhaps such blockheads as some may conceive, considered poetical quotation as one of the requisite ornaments of oratory. – Isaac D’Israeli, “Quotation,” A Second Series of Curiosities of Literature

My quarrel with him is, that his works contain nothing worth quoting; and a book that furnishes no quotations, is me judice, no book,—it is a plaything. – Thomas Love Peacock, Crotchet Castle, 1831 (The Rev. Dr. Folliott)

That part of a work of one author found in another is not of itself piracy, or sufficient to support an action; a man may adopt part of the work of another; he may so make use of another’s labors for the promotion of science and the benefit of the public. – Lord Ellenborough, quoted in Bouvier’s Law Dictionary by John Bouvier, 8th

Then your words of abuse today may turn into a universally valid principle of denigration, for words are magical formulae. They leave fingermarks behind on the brain, which in the twinkling of an eye becomes the footprints of history. One ought to watch one’s every word. – Franz Kafka, quoted by Gustav Janouch, Conversations with Kafka