Kantate, BWV 136 "Erforsche mich, Gott, und erfahre mein Herz"

Erforsche mich, Gott, und erfahre mein Herz (Search me, God, and know my heart), BWV 136 is a church cantata by Johann Sebastian Bach. Bach composed the cantata in 1723 in Leipzig to be used for the eighth Sunday after Trinity. He led the first performance on 18 July 1723.

The work is part of Bach's first annual cycle of church cantatas; he began to compose cantatas for all occasions of the liturgical year when he took up office as Thomaskantor in May 1723. The cantata is structured in six movements: two choral movements at the beginning and end frame a sequence of alternating recitatives and arias. The opening movement is based on a verse from Psalm 139; the closing chorale on a stanza from Johann Heermann's hymn "Wo soll ich fliehen hin". The cantata is scored for three vocal soloists (alto, tenor and bass), a four-part choir, corno, two oboes, strings and basso continuo.