MALVOLIO: In my stars I am above thee, but be not afraid of greatness. Some are born great, some achieve greatness, and some have greatness thrust upon ’em.

William Shakespeare (1564–1616) English dramatist and poet

Twelfth Night, Act 2, Sc. 5, l. 147ff (2.5.147-150) (1601)
    (Source)

The phrase appears three times in the play:

1. As above, Malvolio reading the forged love letter from Maria.
2. Act 3, sc. 4, l. 42ff, Malvolio recalling the phrases from the letter.
3. Act 5, sc. 1, l. 393ff, the Fool reciting the second half of the phrase.

See also Boorstin.