“We must not make a scarecrow of the law,
Setting it up to fear the birds of prey,
And let it keep one shape, till custom make it
Their perch and not their terror.”

—William Shakespeare, Measure for Measure, Act 2, Scene 1.

Sources:

http://www.shakespeare-online.com/plays/measure_2_1.html

http://shakespeare.mit.edu/measure/measure.2.1.html

http://www.bartleby.com/70/1421.html