“Letter to Central Association of German Citizens of the Jewish Faith, 3 [5] April 1920, as quoted in Alice Calaprice, The Ultimate Quotable Einstein (2010), p. 195; citing Israelitisches Wochenblatt, 42 September 1920, The Collected Papers of Albert Einstein, Vol. 7, Doc. 37, and Vol. 9, Doc 368.”

Source: Wikiquote