O Magnum Mysterium composed by Morten Lauridsen
I had the privilege of singing this in college, and every time I hear it I find myself in a state of reverence. Simply beautiful. Here are the lyrics with translation.
O magnum mysterium,
et admirabile sacramentum,
ut animalia viderent Dominum natum,
jacentem in praesepio!
Beata Virgo, cujus viscera
O great mystery,
and wonderful sacrament,
that animals should see the new-born Lord,
lying in a manger!
Blessed is the Virgin whose womb
was worthy to bear
Christ the Lord.