 In this office he printed the Gospel and other Christian books in the Judæo-German dialect, and distributed them among the Jews, with the assistance of the Jewish physician Dr. Heinrich Christian Immanuel Frommann, who translated the Gospel of Lukas with commentary, which was revised and reprinted by Raphael Biesenthal in the 19th century.Frommann's records named him only as typist, but Callenberg was not proficient in Hebrew at all.His first interest was Islam and by travelling got in touch with Jews.