A great mystery

O magnum mysterium et admirabile sacramentum
ut animalia viderent Dominum natum
jacentem in praesepio.

Beata virgo cujus viscera
meruent partare Dominum Christum.
Alleluia.

Translation
O great mystery and wonderful sacrament
That animals see the Lord born
Lying in a manger.

Blessed virgin whose womb
Was worthy to bear Lord Christ.
Allelujah.