In Germany, they came first for the Communists, And I didn’t speak up because I wasn’t a Communist;
And then they came for the trade unionists, And I didn’t speak up because I wasn’t a trade unionist;
And then they came for the Jews, And I didn’t speak up because I wasn’t a Jew;
And then . . . they came for me . . . And by that time there was no one left to speak up."

- Martin Niemöller

Wikipedia has an interesting article about the variations in the text.