English summary: Philipp Jakob Spener was the founder of the pietist movement. His letters are very important for the research on the early modern age, not only for church history but also for social history and the history of ideas. Volume III of the "Dresdner Briefe" contains 141 letters, in which particularly the emergence of the term "pietists" is presented and also the controversy between Spener and the Elector Johann Georg III of Saxony...