O Virgo Virginum quomodo fiet istud: quia nec primam similem visa es nec habere sequentem: filiae hierusalem quid me admiraninimi divinum est mysterium hoc quod cernitis.
O Virgin of Virgins, how shall this be? For neither before was there any like you nor will there be any to follow after: daughters of Jerusalem, why marvel at me? That which you believe is a divine mystery.
Yes, this is the disputed "eighth" O Antiphon, not currently in use in the Divine Office. Some scholars believe that it was originally included in a larger set of "O Antiphons" of which we currently only have and use seven. Other scholars argue that, despite the earliest records of the O Antiphons including O Virgo, due to the sacredness of the number seven, this antiphon is not indigenous to the seven that come down to us today. Perhaps the two most striking differences between this antiphon and the other seven are that this one is addressed to Mary and, due to this, it lacks the "Veni" clause.
Be it original or fabricated, this is a beautiful text. It points toward Our Lady at the very moment of the Incarnation and, at the same time, it points away from her -- "why marvel at me?" -- and it points toward him who is about to be born. Yes, that which we behold, which Mary carried in her womb, is a divine mystery. It is this for which we have been preparing our hearts and our homes: this grand mystery of God made man. Let him find us ready when he comes. Let him find in our hearts a place worthily prepared for him. And let us welcome anew this divine mystery, which Mary and Joseph were privileged to hold in their arms.