Bach's Actus tragicus

J.S. Bach composed the cantata Gottes Zeit is die allerbeste Zeit ("God's time is the very best time") around 1707, when he was a young man.  As Ken Myers observed in his column,

[It] is both a musical and theological tour de force. In this 20-minute-long work (also known as Actus tragicus) Bach organizes biblical texts, Lutheran melodies, and instrumental textures to convey the comforting message of the gospel in the face of death. ... This remarkable and confidently assuring work should be much better known than it is. So now: go hear it. Be comforted and amazed.

See, for instance, this video of a performance by the Netherlands Bach Society.