Ich lasse dich nicht, du segnest mich denn , BWV 157

Ich lasse dich nicht, du segnest mich denn (I will not let you go, except you bless me), BWV 157, is a church cantata by Johann Sebastian Bach. He composed it in Leipzig in 1726/27. The first known performance was on 6 February 1727 in Pomßen.

The work is not to be confused with the motet Ich lasse dich nicht, BWV Anh. 159, which is probably by Bach and which takes its title from the same biblical quotation.

The work appears to have been commissioned as a funeral cantata for Johann Christoph von Ponickau (1652–1726), a Saxon chamberlain. Picander, Bach's librettist, clearly linked the cantata to Ponickau, publishing an extended funeral ode on his death, followed by the text of the cantata. The first known performance was at a memorial service for Ponickau on February 6, 1727 in the church of his home village, Pomßen (20 km from Leipzig). The event is quite well documented in that there a printed commemoration sermon giving some information about the music performed, which included a second Bach cantata, now lost (Cantata BWV Anh. 209). We do not know if Bach was present, although some writers assume so.

The cantata appears to have been adapted for performance as part of Leipzig's church music, specifically for the Feast of the Purification of Mary which was celebrated on 2 February. The existence of more than one version is implied in the earliest surviving manuscripts, from after Bach's death, copied by Christian Friedrich Penzel. The primary surviving score dates from 1755 and there are parts from the 1760s.

The prescribed readings for the feast day were from the book of Malachi, "the Lord will come to his temple" (Malachi 3:1–4), and from the Gospel of Luke, the purification of Mary and the Presentation of Jesus at the Temple, including Simeon's canticle Nunc dimittis (Luke 2:22–32). The idea from Simeon's canticle to depart in peace has often been used as an image for the death of a Christian. Picander included a quotation from Genesis (Genesis 32:26–32) in the first movement and the last stanza of the hymn "Meinen Jesum laß ich nicht" by Christian Keymann in the fifth movement.

The work is scored for tenor and bass vocal soloists, four-part choir, flute, oboe, oboe d'amore, two violins, viola, and basso continuo.

The work has five movements:

The opening movement sets only a single line: the biblical quotation from Genesis which became the title of the cantata. The movement has an eight-measure ritornello that opens, ends, and bisects the movement; it features a prominent imitative motif.

The second movement is a tenor aria accompanied by continuo and obbligato oboe d'amore, which perform a long ritornello serving much the same structural function as in the first movement. Craig Smith suggests that this is "perhaps the single most difficult tenor aria in the whole repertoire", with "wild and extremely ornate melismas".

The tenor recitative is scored for strings and continuo. It recalls some of the motivic material from the first movement.

The fourth movement combines elements of aria, recitative, and arioso. It opens with a ritornello of violin, flute and continuo. Structurally, the movement completes most of a da capo aria before a recitative episode interrupts the reprise of the A section. The music moves between aria and recitative twice more before a final aria section ends the movement.

The cantata ends with a four-part setting of the chorale with a conjunct melody and active continuo line.