This is the melody to which Gurnemanz proclaims, Gesegnet sei, du Reiner durch das Reine! It is derived from the beheaded Redemption motif (#1D).
Gesegnet sei, du Reiner durch das Reine!
The first phrase of this theme is similar to Tristan's O sink' hernieder, Nacht der Liebe.
O sink' hernieder, Nacht der Liebe