Complex sentence: He used the melody several times in his "Christmas Oratorio" (1734), for instance the chorale "Ach, mein herzliebes Jesulein", which uses stanza 13 of Luther's "Vom Himmel hoch" as text, closes Part I of the oratorio.
Split into simpler sentences: He used the melody several times in his "Christmas Oratorio" (1734). The chorale "Ach, mein herzliebes Jesulein", which uses stanza 13 of Luther's hymn, closes Part I of the oratorio.