Most of the cantatas Bach wrote during his tenure in Weimar are to texts of Salamo Franck, the head of the mint at the Weimar court. Franck is the best of all the poets that Bach set, and our cantata today BWV 165 is one of his greatest works. The subject is the purification of the human spirit by baptism, and Franck constructs a moving and poetic set of images to discuss this difficult topic.
The opening soprano aria uses the image of bath water as the purifier of the soul and as the inscriber in the book of life. Bach’s music is both watery and visionary. The fugue for strings and soprano voice resembles some of the ethereal slow fugues found in the Well-Tempered Clavier. The religious ecstasy achieved at the words “and grants us the new life” is breathtaking even for Bach.
The first bass recitative vividly characterizes both the guilt of the sinner and the radiance of being clothed in the “white silk of Christ’s innocence.” The alto aria is disciplined in its utterance. The slow motor of the continuo acts like a prayer wheel, a sure and steady path to salvation. The ecstasy returns in the marvelous accompanied recitative again for bass. It should be noted that there are two separate snake references. The first is the more common image of Satan. The second, the “blood-red serpent image” refers to a common medieval portrayal of Christ in Limbo as a snake on the cross. This was already an archaic metaphor in Bach’s day but the church at Weimar had a well-known icon with this image. The reference was thus clear to parishioners there. The obbligato for all the violins in the tenor aria snakes along and clearly has the both Satanic and the Christ-like function. A harmonization of “Nun lasst uns Gott, dem Herren” completes the cantata.