This quotation is often cited incorrectly. The exact phrasing was supplied by Sibylle Sarah Niemoeller von Sell, Martin Niemoeller's wife. The remark was made in reply to a student's question, "How could it happen?"
“First they came for the Communists, but I was not a Communist so I did not speak out. Then they came for the Socialists and the Trade Unionists, but I was neither, so I did not speak out. Then they came for the Jews, but I was not a Jew so I did not speak out. And when they came for me, there was no one left to speak out for me.”