Abstract
The main focus of the article is on the opening chorus of the cantata BWV 21 and its numerous and striking text repetitions. The article reveals that Johann Sebastian Bach was guided in his composition by a pietism typical of the time. To prove this, a wide variety of pietistic-historical writings is presented. This research clarifies two matters: the determination of the cantata in the liturgical year becomes clear and Mattheson’s famous critique of the text repetitions can now be discussed more adequately.