172. Bass recitative The bass next sings "" (Only consider, child of God) as a secco recitative ending in an arioso, the typical style of recitatives during the Weimar period. It adopts canonic imitation between the voice and continuo parts. The interaction illustrates the unity of Christians with Jesus that the text reflects: "dass Christi Geist mit dir sich fest verbinde" (that the spirit of Christ may be firmly united with you). The mystical element of this unity, which is also exemplified in the subsequent aria and the later duet, contrasts with the "combative" character of the outer movements, where the hymn tune prevails. Soprano aria The fourth movement, "" (Come into my heart's house) is a soprano aria with a continuo ritornello. It is characterized by extensive melismas and a "floating and ethereal" melody. The soprano also sings the continuo melody. Central chorale The central chorale presents the third stanza of the hymn, "" (And if the world were full of devils). The chorale melody is sung in unison voices, an unusual practice for Bach. The melody is unadorned and in 6/8 time. The orchestral accompaniment becomes more agitated and complex as the movement progresses. Tenor recitative The tenor recitative, "" (Then stand with Christ's bloodstained flag) is secco; like the earlier bass recitative, it concludes with an arioso. The movement includes "occasional furious melismas" used to underscore the sense of joy conveyed by the words. Aria duetto An alto and tenor duet, "" (How happy are they, who bear God in their mouths) is accompanied by continuo and obbligato violin with oboe da caccia. The movement is "submissive" in character with a texture that becomes more complex as the duet progresses, at one point including five simultaneous melodic lines. Bach uses a juxtaposition of "flowing, largely semi-quaver" instrumental parts with the vocal "crotchet/quaver rhythms" to depict the shield of the faithful; the two parts then coalesce to tell of the smiting of enemies. Closing chorale The final movement is a four-part setting of the last stanza of the hymn, "" (That word they must allow to stand). Also in D major, each of the SATB lines is doubled by one or more instruments, and each part has a smaller vocal range than in other movements to make them simpler for the congregation to sing. Each phrase ends with a pause to break up the structure, although these are