The Presanctified liturgy enters written law at the Council in Trullo, held in Constantinople in 692, whose fifty-second canon directs that on the days of the holy fast, except Saturdays, Sundays and the feast of the Annunciation, the liturgy of the presanctified is to be celebrated. The canon regulates an existing custom rather than inventing one, so the practice is older than its legislation, and historians trace the underlying habit to the early Christian custom of the faithful keeping the reserved sacrament for weekday communion at home, a private usage the church gradually gathered into a public evening service. The attribution history is a small comedy of ecclesiastical exchange. Greek manuscripts transmit the service anonymously or under various names, but the Slavic books assign it to Gregory the Dialogist, the same Gregory the Great who reigned as pope of Rome from 590 to 604 and whose Dialogues gave him his Eastern surname.
The legend grew from Gregory's genuine reputation in the East and from traditions about his liturgical work in Rome, where a presanctified communion rite also existed on Good Friday; scholarship finds no evidence connecting him to the Byzantine service. The Roman Rite, for its part, kept its own presanctified rite on exactly one day of the year, Good Friday, which it retains still, so the two halves of Christendom each preserve a version of the same ancient instinct, one annually and one throughout Lent.