Communing from the Body and Blood of the Master during the period of spiritual combat.
The Liturgy of the Presanctified Gifts is attributed to Saint Gregory the Dialogist (†604), Pope of Rome, but in actuality, it is not the work of one individual, but is a composite work coming down to us from Holy Tradition.
The Liturgy of the Presanctified Gifts, which consists of the Service of Vespers and the Communion of the Faithful with the Holy Gifts. It is commonly celebrated daily in monastic communities, and on Wednesdays and Fridays in parishes, with Holy Bread—that is, the Body of Christ—which has been intincted in the Holy Blood and consecrated at the preceding complete Liturgies on Saturdays or Sundays. The Presanctified or “abridged” Divine Liturgy (since it is affixed to Vespers), is normally celebrated in the late afternoon, when Christians, having fasted until that time, commune, afterwards eating a meal of dry foodstuffs (dried fruits and nuts).
The celebration of the Divine Liturgy, because it is festive and Resurrectional in character, is not allowed during Great Lent and the somber period of the fast, according to ancient tradition and the forty-ninth Canon of the Synod of in Laodiceia . However, from their side, the faithful children of the Church, engaged in the abstemious struggle of the Great Fast and having a clear and particular need for reinforcement by the Holy Mysteries during this period of intensive spiritual combat, desired to commune as often as they could, since Holy Communion was indeed their life and sustenance.
For this reason, so that the faithful not be deprived of the Holy Eucharist on the weekdays of the Great Fast, but that they might be able to commune from the Presanctified Holy Bread [the Body if Christ], the Church, by way of the fifty-first Canon of the Fifth-Sixth [Quinisext] Synod , appointed that the Divine Liturgy of the Presanctified Gifts take place on the weekdays of the Great Fast.
Saint Nikodemos the Hagiorite [†1809], in his Rudder, citing the Byzantine canonologist Matthew Blastaris [fl.14th century], reminds us that the faithful resemble wrestlers, and just as wrestlers cease their matches in the afternoon to take nourishment in order to strengthen themselves for the upcoming bout, so the faithful commune from the Body and Blood of the Master during the period of spiritual combat in the Great Fast, that they might be reinvigorated and reinforced by the Lord, thus to continue their match against the passions and the spiritual enmity of the devil with renewed powers and more valorously.