I first heard this piece my Freshman year of college, when the student-led (and very amateur) choir tried to learn it. There were no more than ten of us, on a good night, and we did not have enough voices for all of the parts, but even obscured by our poor efforts, the music nearly brought me to tears. It is haunting, and, somehow, the notes and harmonies seem to declare the message as clearly as the words.
Ubi caritas et amor, Deus ibi est.
So simple, and yet... endlessly complex, a deep mystery of the Christian life...