During the evening prayer of the Liturgy of Hours, which is also known as Vespers, the Church prays the beautiful prayer of Mary known as the Magnificat. Preceding the Magnificat, there is an antiphon which is simply a short verse which connects the prayer to the particular feast day or liturgical season. On the last seven days of Advent, from December 17th through December 23rd, the antiphon for Vespers is one of the so-called "O Antiphons". It is related to a particular title of Christ's, and the antiphon ends with a plea for the Messiah to come.

December 17th

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, coming forth from the mouth of the Most High,
reaching from one end to the other,
mightily and sweetly ordering all things:
Come and teach us the way of prudence.

And the Spirit of the LORD shall rest upon him, the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and the fear of the LORD. And his delight shall be in the fear of the LORD. Isaiah 11:2

This also comes from the LORD of hosts; he is wonderful in counsel, and excellent in wisdom. Isaiah 28:29