PORTIA: How far that little candle throws his beams!
So shines a good deed in a weary world.

William Shakespeare (1564-1616) English dramatist and poet

Merchant of Venice, Act 5, sc. 1, l. 99ff (5.1.99-100) (1597)
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In some versions, "So shines a good deed in a naughty world."

Sometimes misattributed to Roald Dahl (or even Gene Wilder); the character Willy Wonka uses the second sentence toward the end of the film Willy Wonka and the Chocolate Factory (1971).