Costly thy habit as thy purse can buy,
But not expressed in fancy—rich, not gaudy,
For the apparel oft proclaims the man,
And they in France of the best rank and station
Are of a most select and generous chief in that. (1.3.70-75)
These lines are from Shakespeare's Hamlet, in which Polonius advises his son Laertes to be conservative in his conduct and clothing before he leaves for France--ironically, of course, because Polonius himself is a meddler and court sycophant. The old courtier cautions his son to be wise in his tastes and behavior, speaking in platitudes. His line that "apparel oft proclaims the man" is expressed in modern times as "The clothes make the man"; meaning that people form judgments about others based upon the clothes that they wear. Polonius instructs Laertes that he will appear to be noble if he so dresses, especially in France where appearances are everything.
A hilarious example of this statement of Polonius is found in another of Shakespeare's plays, Tweflth Night. In this comedy which is about the inversion of social and personal expectations, a pratical joke is played upon a sour, humorless Puritan named Malvolio. He is convinced by others that if he wears yellow stockings and crossed garters, he will win the love of Olivia, a beautiful noblewoman he desires. Instead, she laughs at his foolish clothing, thinking him mad.