This Richard Strauss song is one of the Vier Letzte Lieder (“Four Last Songs”) composed by Richard Strauss in 1948. They really were his last songs, and he never heard them performed.
My favorite is Beim Schlafengehen (“On going to sleep”), clearly about death. And the best version, by far, is by soprano Jessye Norman. Her voice is almost inhumanly powerful, and the song ineffably beautiful. The crescendo, at 3:10, and the ending, always make me tear up. If you don’t like this, you don’t have ears to hear:
If I can hear music on my deathbed, this is the song I want them to play.