The second time the fragment occurs, the cellos support it with a downward run:

The moment of conception takes place beneath the fragment’s third occurence, as Bach combines syncopation and run in a hybrid figure:

In assigning this figure to the choral basses as well as the cellos, and beginning it in the prominent upper portion of the basses’ range, he invites us to notice it .

When we next encounter this figure, some ten measures later, Bach has developed it into something more motivic. He presents it here in the upper portion of the tenors’ range, where we couldn’t fail to notice it if we tried: