Erhalt uns, Herr, bei deinem Wort (Sustain us, Lord with your word),[1] BWV 126, is a cantata by Johann Sebastian Bach for use in a Lutheran service.

Bach structured the cantata in six movements and scored it for three vocal soloists, a four-part choir and a Baroque instrumental ensemble of trumpet, oboe, strings and continuo.

[5] The result are seven stanzas: A line in the epistle, "For the word of God is quick and powerful, and sharper than any two-edged sword" (Hebrews 4:12), possibly prompted the choice of the hymn.

Instead of relating closely to the parable, the poet concentrates on a general request to God: to keep his people faithful to his word, to protect them from enemies and to provide peace.

Bach scored the work for three vocal soloists (alto (A), tenor (T) and bass (B)), a four-part choir, and a Baroque instrumental ensemble: trumpet (Tr), two oboes (Ob), two violins (Vl), viola (Va), and basso continuo (Bc).

A characteristic feature of the instrumental concerto is a four-note trumpet signal, which is derived from the beginning of the chorale melody, as if to repeat the words "Erhalt uns, Herr" (Sustain us, Lord) again and again.

[13] The Bach scholar Christoph Wolff notes that the trumpet fanfare "underlines the combative, dogmatic character of this late devotional song of Luther's".

[14] Movement 3 presents two text elements interwoven, the recitative "Der Menschen Gunst und Macht wird wenig nützen" (The wish and will of mankind are of little use),[1] and the interspersed four lines of the hymn's third stanza, "Gott, Heiliger Geist, du Tröster wert" (God, Holy Spirit, worthy Comforter).

John Eliot Gardiner quotes William G. Whittaker: Bach’s "righteous indignation at the enemies of his faith was never expressed more fiercely than in this aria".

[12] The Bach scholar Alfred Dürr describes the movement as an "aria of genuinely baroque dramatic force", expressing "Old Testament zeal".

[14] A tenor recitative, "So wird dein Wort und Wahrheit offenbar" (Thus Your word and truth will be revealed),[1] changes the topic and leads to peace, implored in the final movement.