17th December, O Sapientia!

O Sapientia, quae ex ore Altissimi prodiisti, attingens a fine usque ad finem, fortiter, suaviterque disponens omnia; veni ad docendum nos viam prudentiae.

O Wisdom, that proceedest from the mouth of the Most High, reaching from end to end mightily, and disposing all things with strength and sweetness! come and teach us the way of prudence.

The Church enters to-day on the seven days, which precede the Vigil of Christmas, and which are known in the Liturgy under the name of the Greater Ferias. The ordinary of the Advent Office becomes more solemn; the Antiphons of the Psalms, both for Lauds and the Hours of the day, are proper, and allude expressly to the great Coming. Every day, at Vespers, is sung a solemn Antiphon, which consists of a fervent prayer to the Messias, whom it addresses by one of the titles given him by the sacred Scriptures.

In the Roman Church, there are seven of these Antiphons, one for each of the Greater Ferias, They are commonly called the O's of Advent, because they all begin with that interjection.

The canonical Hour of Vespers has been selected as the most appropriate time for this solemn supplication to our Saviour, because, as the Church sings in one of her hymns, it was in the Evening of the world (vergente mundi vespere) that the Messias came amongst us. These Antiphons are sung at the Magnificat, to show us that the Saviour, whom we expect, is to come to us by Mary. They are sung twice; once before and once after the Canticle, as on Double Feasts, and this to show their great solemnity.

These admirable Antiphons, which contain the whole pith of the Advent Liturgy, are accompanied by a chant replete with melodious gravity, and by ceremonies of great expressiveness. Let us enter into the spirit of the Church; let us reflect on the great Day which is coming; that thus we may take our share in these the last and most earnest solicitations of the Church imploring her Spouse to come, and to which He at length yields.

These antiphons are the inspiration behind the popular Advent Hymn: O come, O come Emmanuel.

O come, thou wisdom from on high

Who madest all in earth and sky,

Creating us from dust and clay:

To us reveal salvation's way.

Rejoice! Rejoice! Emmanuel

shall come to thee, O Israel.

The Catholic Encyclopaedia on the O Antiphons: http://www.newadvent.org/cathen/11173b.htm