It was a delight to sing this incredibly beautiful Zum Sanctus as a member of Die Zeitlupe at a memorable "Tischabendmahl" on Maundy Thursday in 2006 in Michaelskirche Bremen-Grohn. It was composed by Franz Schubert and is a part of his Deutsche Messe D.872. Written in E♭-major it is performed very slowly and takes about 3 minutes.
It may be found in Deutsche Messe D.872: Full Score.

Score