None, however attentive, can always discover that merit which indigence or faction may happen to obscure, and none, however powerful, can always reward it.
 Samuel Johnson, The History of Rasselas, Prince of Abissinia (1759). copy citation

Context

““which is thus unreasonable, I hope that I shall always have spirit to despise and you power to repress.” “Discontent,” answered Rasselas, “will not always be without reason under the most just and vigilant administration of public affairs. None, however attentive, can always discover that merit which indigence or faction may happen to obscure, and none, however powerful, can always reward it. Yet he that sees inferior desert advanced above him will naturally impute that preference to partiality or caprice, and indeed it can scarcely be hoped that any man, however magnanimous by Nature or exalted by condition, will be able to persist for ever in fixed and inexorable justice of distribution;” source