The Mystery of the Maiden's belly

"The more widely used form."  That is the description in Common Worship: Time and Seasons of the usage by which the Advent antiphons begin on the 17th December rather than the 16th, as in the Kalendar of the BCP 1662.

Now, of course, the statement is factual - the 17th is "the more widely used form", normative in the Latin rite.  The 16th was the use of Sarum, an oddity in a local rite.  But there is something richer here than liturgical antiquarianism. The 16th allowed for an addition to the Advent antiphons, on the 23rd:

O Virgin of virgins, how shall this be?
For neither before thee was any like thee, nor shall there be after.
Daughters of Jerusalem, why marvel ye at me?
The thing which ye behold is a divine mystery.

Here the Church's Advent prayer rejoices in the fulfilment of the yearnings expressed from O Sapientia.  The fulfilment comes not in abstractions, but in the swollen belly of the Maiden.  There, the Church's Advent prayer and longings are answered.

In the words of Rowan Williams:

Somehow the whole history of God's ancient people comes into focus here, the history of a people who have received grace and gifts from God and who have had to 'take responsibility' for God in the world.  All that God has given to his chosen community is gathered to a point as Mary is asked if she will take responsibility in a unique for God in the world.

Similarly, Robert Jenson says:

As the created space for God, Mary is Israel concentrated ... Mary is Israel in one person.

The longings of Israel, which become the Church's Advent prayer, are not answered by universal abstractions, but in the flesh and blood of the Maiden's womb.  The antiphon O Virgo virginum draws us into this mystery, beautifully preparing us for the celebration of the Nativity of our Lord - this Child, born of this Virgin, is Wisdom, Adonai, Root of Jesse, Key of David, Morning Star, King of the Gentiles, Emmanuel.  

O Virgo virginum, then, brings us on this day before Christmas Eve to still ourselves before the Crib, awaiting the Maiden's Child, in whom all longings and desires are met. As Malcolm Guite says in his sonnet for this antiphon:

O Maid amongst the maidens, turn your face,

For when we glimpse you we are not alone.

This is the assurance given to us in the belly of the Maiden of Nazareth.  We are not alone. God is with us.

Is there a more fitting prayer or anthem to draw Advent to a close?  In maintaining the Sarum use of O Sapientia on the 16th December, the BCP Kalendar bestows on Anglicanism a precious gift for Advent.  With O Virgo virginum, we rejoice with the Maiden in the Child she carries, the One who is the Advent hope.