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

A knowledge of general literature is one of the evidences of an enlightened mind; and to give an apt quotation at a fitting time, proves that the mind is stored with sentential lore that can always be used to great advantage by its possessor. – James Ellis, quoted in Day’s Collacon: An Encyclopædia of Prose Quota

One is more apt to become wise by doing fool things than by reading wise sayings. – Robert Brault, rbrault.blogspot.com

A learned historian declared to me of a contemporary, that the latter had appropriated his researches; he might, indeed, and he had a right to refer to the same originals; but if his predecessor had opened the sources for him, gratitude is not a silent virtue. – Isaac D’Israeli, “Quotation,” A Second Series of Curiosities of Literature