A prefeast (also known as forefeast) is a period of time preceding certain major feasts of the Christian year during which the Church anticipates the approaching Feast. The liturgical life of the Church reflects this anticipation by foreshadowing the feast in the divine services leading up to the Nativity.
This service is a combination of Vespers (evening prayers) and Compline (final service of the day, before sleep) and incorporates beautiful hymnography to prepare us for the birth of Christ.
On this day we sing;
Let us celebrate, O people
The prefeast of Christ's Nativity!
Let us raise up our minds on high,
Going up in spirit to Bethlehem,
Let us behold the great mystery in the cave,
For Eden is opened once again
When God comes forth from a pure Virgin,
Remaining the same perfect God and becoming perfect man.
Therefore let us cry out to Him:
Holy God, Father without beginning!
Holy Mighty, Incarnate Son!
Holy Immortal, the Spirit and Comforter!
O Holy Trinity, glory to Thee!