(My attempt at a translation: You who are so French, I sense that you are doubly in mortal danger, because you are a Frenchman, and because you are a Jew.)
Source: Antoine de Saint-Exupéry, Lettre à un otage (“Letter to a Hostage”), first published in 1943. (My copy lists a 1944 copyright.)
There’s more about this text, and Saint-Exupéry’s friendship with Léon Werth, the titular though never-named hostage, in Stacy Schiff’s Saint-Exupéry biography. (Werth is the same friend to whom Saint-Exupéry dedicated Le Petit Prince.) I am currently awaiting the arrival of one of Werth‘s works about the wartime period, 33 Jours.