Although Brahms was an agnostic, he kept Luthers Bible by his bed and turned to it for musical inspiration, the greatest of which was his German Requiem. Early in his career, Jo ran a choral society whose slogan, which he invented, was Fix oder nichts. Perfect or nothing. Brahms wrote a lot of music for his singers, and this is one of his religious pieces. Its written for organ and female chorus; it looks back to Bach and Palestrina.
I am not a big fan of Brahms, but that is exquisite.