Do not hold as gold all that shines as gold.

"All that glitters is not gold." Cf. Chaucer, The House of Fame, bk. I, l. 272, and The Canon's Yeoman's Tale, l. 409; Lydgate, On the Mutability of Human Affairs, l. 12; Shakespeare, The Merchant of Venice, act II, sc. vi, l. 65; Cervantes, Don Quixote, pt. II, bk. iii, ch. 33; Middleton, A Fair Quarrel, act V, sc. i; Dryden, The Hind and the Panther, pt. I, l. 214; Gray, On the Death of a Favourite Cat, st. 7; Tolkien, The Fellowship of the Ring (Strider's riddle)