Who wrote Flosst mein Heiland by Christmas Oratorium by J. S. Bach ?

Question

Who wrote Flosst mein Heiland by Christmas Oratorium by J. S. Bach ?

Answer 1

"Flosst, mein Heiland" is actually an aria from the Christmas Oratorio itself (or rather, is found in one of the cantatas that make up that larger work), and thus was itself written by J.S. Bach.

Perhaps I misunderstood your question - I don't know if Bach borrowed the tune from a pre-existing work. Maybe someone else can help out there.