Darzu ist erschienen der Sohn Gottes (For this the Son of God appeared),[1] BWV 40, is a church cantata by Johann Sebastian Bach.

The title of the cantata also appears in more modern German as Dazu ist erschienen der Sohn Gottes.

The cantata text by an unknown author is not related to the martyrdom, but generally reflects Jesus as the conqueror of sin and the works of the devil.

Movement 7 finally picks up a line from the day's Gospel, verse 37, "how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings".

In this cantata, the first insertion is from a hymn that Bach would later use at the end of Part III of his Christmas Oratorio,[6] sung to the earlier melody (1589) by an anonymous composer.

[8] The closing chorale is sung to a melody by Andreas Hammerschmidt, published in his collection Vierter Theill Musicalischer Andachten (Fourth part of musical meditations) in Freiberg, Saxony (1646).

For the Christmas season of 1723, from the First Day of Christmas to Epiphany, Bach had performed a program of six cantatas, five of them new compositions, and two major other choral works: The cantatas were performed twice on the principal feast days, in the main service, alternating in one of the two major churches of Leipzig Thomaskirche and Nikolaikirche, and in the vespers service in the other.

[12] For the festive occasion, the cantata is scored for three vocal soloists—alto, tenor and bass—a four-part choir, two horns (corno da caccia), two oboes, two violins, viola and basso continuo.

[6] The opening chorus in F major is a setting of the short text "Dazu ist erschienen der Sohn Gottes, daß er die Werke des Teufels zerstöre."

[18] John Eliot Gardiner, who conducted this and other Christmas cantatas during the Bach Cantata Pilgrimage with the Monteverdi Choir in 2000, compares the movement's style to the stilo concitato (excited style) of Claudio Monteverdi and notes its "vigorous endorsement to the military campaign against sin and the devil instituted with Jesus' birth".

[17] The short secco recitative, sung by the tenor, the typical voice for Evangelist narration, delivers the message "Das Wort ward Fleisch und wohnet in der Welt" (The word became flesh and lived in the world).

)[1] is accompanied by both horns and oboes[18] and stresses the words "freuet" (be glad) by extended coloraturas and "erschrecken" (terrify) by sudden rests.