Johann Sebastian Bach composed the church cantata Gott der Herr ist Sonn und Schild (God the Lord is sun and shield),[1] BWV 79, in Leipzig in 1725, his third year as Thomaskantor, for Reformation Day and led the first performance on 31 October 1725.

Bach began the libretto for the feast with a quotation from Psalm 84 and included two hymn stanzas, the first from Martin Rinckart's "Nun danket alle Gott", associated with Reformation Day in Leipzig, as the third movement, and as the last movement the final stanza of Ludwig Helmbold's "Nun laßt uns Gott dem Herren".

Bach composed a work of "festive magnificence", structured in six movements, with an aria following the opening chorus, a pair of recitative and duet following the first chorale.

He scored the work for three vocal soloists, a four-part choir, and a Baroque instrumental ensemble of two horns, timpani, two transverse flutes (added for a later performance), two oboes, strings and continuo.

He scored the work for three vocal soloists (soprano, alto, bass), a four-part choir and a Baroque instrumental ensemble of two horns (Co), timpani (Ti), two flauto traverso (Ft), two oboes (Ob), two violins (Vl), viola (Va), and basso continuo.

As Hofmann points out, Bach achieved "festive magnificence",[5] using two horns and timpani not only in the opening chorus but also as obbligato instruments in the two chorales.

[5] The cantata opens with a choral movement, "Gott der Herr ist Sonn und Schild" (God the Lord is sun and shield).

The horns are silent in the middle section, but the voices enter "an imitative discussion of a simplified version of the string theme from the ritornello.

[8] John Eliot Gardiner, who conducted during his Bach Cantata Pilgrimage in 2000 the cantatas for Reformation at the Schlosskirche in Wittenberg where the Reformation began, describes the opening chorus as a ceremonial procession, and hears the "insistent drum beat" going along with the "fanfares of the high horns" as "the hammering of Luther’s theses to the oak door at the back of the church".

[9] The only recitative, sung by the bass, "Gottlob, wir wissen den rechten Weg zur Seligkeit" (Praise God, we know the right way to blessedness),[1] mentions the reason for thanks on this occasion.

The phrase "Du hast uns durch dein Wort gewiesen" (You have instructed us through Your word)[1] addresses "the basic issues of the Reformation", as Rilling points out.

[8] Gardiner hears in the "innocent" setting of the voices "a pre-echo … of Papageno and Papagena, a Mozartian impression, reinforced by the hint of Eine kleine Nachtmusik in the violin ritornelli".