From: Office for the Liturgical Celebrations of the Supreme Pontiff
As has been noted, in the worship of the early Christians there were present: preaching, the reading of Sacred Scripture, prayers, hymns for a didactic purpose.
In the year 150, Saint Justin, in his Apology and in his Dialogue with Trypho, gave the first description of the Roman Mass, divided into two parts: the "didactic" part, made up of readings from the Prophets and the Apostles and the "sacrificial" part focused on the Passion of the Lord.
Greek was used in the liturgy; the use of Latin came in toward the fourth century; before the fourth century here and there the readings were customarily read in Greek, and afterwards translated into Latin; thus an almost bi-lingual Mass existed. Thus, the custom of proclaiming the readings of the Mass in Greek seems simply to have originated from the need to promote participation among those faithful who could not yet understand Latin.
Nevertheless, the on-going development of the primacy of the Bishop of Rome, from the time of Saint Ignatius of Antioch who, in the second century, defines the Church of the City of Rome as the Church that “presides in charity,” and likewise that the universal Church is an organic body built on mutual charity, will have an influence on the preservation of certain parts of the Papal Liturgy in Greek – an indication of the Pope's solicitude for the all the churches, in particular the Eastern Churches. For example, still today in the Roman Liturgy of Good Friday one sings the Greek chant known as the Trisagion, addressed to the Lord Jesus Christ, Who is thrice-holy, because He is God, the Strong One, the Immortal One, and has mercy on us.
After the schism of 1054 between Rome and Constantinople, the longing for the restoration of unity did not die out; rather, the Supreme Pontiff did not give up the intention of reestablishing the communion of the Eastern Churches with the Apostolic See: one thinks of the Council of Florence and afterwards of the establishment in Rome of the Greek College in 1577 by Pope Gregory XIII. One recalls the institution of the Greek College because this act had its effects, in a certain sense, on the rite of proclaiming the readings in Greek and then in Latin translation. In fact, it was from the Greek College that the Papal Master of Ceremonies used to draw to conduct a bilingual liturgical service.
The detailed description of the rite of proclaiming the Epistle and Gospel in Greek and in Latin in the Papal Liturgy goes back to the last century:
The Apostolic Subdeacon takes from one of the Clerics of the Pontifical Chapel the Epistle Book, and having made a genuflection to the altar and to the Supreme Pontiff, with the assistance of a Pontifical Master of Ceremonies, goes to the far end of the pew, in which the Cardinal Priests are seated, waits until all are seated, and at the sign from the Master of Ceremonies chants the Epistle. He remains there for the duration of the Epistle chanted in Greek. The Epistle having been chanted in Latin, the Subdeacon of the Greek Rite takes from another Cleric of the Pontifical Chapel the Greek Epistle Book, and having carried out the same ceremonies, and assisted by another Pontifical Master of Ceremonies, chants the Epistle next to the Apostolic Subdeacon.
After the chanting of the Epistle in Greek, the Apostolic Subdeacon and that of the Greek Rite, guided by the Pontifical Masters of Ceremonies, go to the papal throne, and having made a genuflection, go up, kissing, one after the other, the foot of the Pontiff; then the deacons genuflect to the Pope and return to the altar, where each one genuflects to the Cross, and returns the Epistle Book to the Cleric of the Pontifical Chapel.
The Subdeacon of the Greek Rite returns to the column of the altar, to the Epistle side, and the Apostolic Subdeacon stops near the Cardinal Deacon who is ministering, and then reads the Epistle and the Gradual. Two Archbishops assisting at the foot of the throne ascend the papal throne with the Book and with the Candle. The Supreme Pontiff reads the Epistle, the Gradual and the Gospel. When the Supreme Pontiff signs the Gospel, the Cardinal Deacon who is ministering, takes off his miter, descends from the altar, and receives the Gospel Book from the Train-bearer. The Cardinal Deacon then, having made the prescribed bows, places the Gospel Book on the altar, and remains near the altar, until the Pope has finished reading. Afterwards the Cardinal Deacon approaches the papal throne, to kiss the hand of the Holy Father.
At the same time, a Pontifical Master of Ceremonies leads the Thurifer-Prelate, who holds the thurible and the boat, to the papal throne, for the imposition of incense. The Cardinal Suburbicarian Bishop holds the boat before the Pope, to whom he offers, with the prescribed kisses the little spoon, asking the Pope for the blessing of the incense with the usual formula.
The Cardinal Deacon who is ministering, having kissed the hand of the Pope, returns to the altar and, having genuflected on the edge of the predella, says the prayer: Munda cor meum, etc.
The Voting Acolytes of the Apostolic Signatura, taking into their hands seven candelabra, stop near the steps leading up to the altar, with the Apostolic Subdeacon standing in their midst.
The Thurifer with the thurible and the boat, returns to the throne at the altar, and places himself near the Prelates who carry candles, on the Epistle side.
The Cardinal Deacon who is ministering, having said the Munda cor meum, takes the Gospel Book from the middle of the altar, descends from there, and places himself to the right of the Apostolic Subdeacon. All genuflect to the Cross, except for the Cardinal Deacon, who makes a profound bow.
Turning around and turning back afterwards, they switch so that the Cardinal Deacon who is ministering, as he proceeds to the throne, would be on the right of the Subdeacon, and at the right of the Cardinal would go the four Acolytes and the three others would be placed to the left of the Subdeacon.
Having arrived before the steps of the throne, all genuflect, except for the Cardinal Deacon who is ministering, who bowing profoundly toward the Supreme Pontiff, asks for the blessing, saying: Iube, Domne, benedicere. The Pope gives him the blessing, responding, Dominus sit in corde tuo, etc.
After the Pope has given the blessing, all stand up, and again genuflect, except for the Cardinal Deacon who is ministering, who makes a profound bow. By the shortest route, they proceed, in the same way from the altar to the throne, near the lectern already prepared by a Cleric of the Pontifical Chapel, near the pew of the Cardinal Deacons, by the altar.
The Thurifer stays with the Pontifical Master of Ceremonies to the left of the lectern, at the back side of which the Apostolic Subdeacon positions himself.
The Prelate Acolytes line up in such a way that four of them are on the right of the lectern and three on the left. The Cardinal Deacon who is ministering stands before the lectern and opens the Gospel Book on it, for the chanting of the Gospel.
Meanwhile, the second Assisting Cardinal Deacon takes the gremial and the miter to the Supreme Pontiff. The Supreme Pontiff rises and remains standing until the chanting of the Gospel has ended.
The Cardinal Deacon who is ministering, sings: Dominus vobiscum and then: Sequentia sancti Evangelii, etc., signing at the same time the Gospel Book and himself. The Thurifer hands the thurible to the Cardinal Deacon who is ministering, who then incenses the Gospel Book, and afterwards returns the thurible to the Thurifer, who remains in the same place, for the chanting of the Gospel in Greek.
The Gospel having been chanted in Greek, the Apostolic Subdeacon takes the Gospel Book and, holding it before his chest, stops at the right of the lectern.
The Pope sits, and the first Assisting Cardinal Deacon hands the miter to the Pope.
Two Acolytes remain hinc inde near the lectern, the other five, having made the required genuflections to the Supreme Pontiff and to the altar, while the Cardinal Deacon who is ministering makes a profound bow, they return to the credence table and put down the candelabra.
The Cardinal Deacon who is ministering, goes to sit at the faldstool and puts on his miter. In the meantime, the Deacon of the Greek Rite takes the Gospel Book from a Cleric of the Chapel, and places it on the mensa of the altar, having made genuflections to the Supreme Pontiff and to the Cross.
Afterwards, the Cardinal Deacon descends immediately and again genuflects to the Cross, goes to the papal throne, genuflects, and goes up to the top step of the throne to kiss the foot of the Pope. The Cardinal Deacon returns to the altar, and while still kneeling in the middle on the highest step, says the prayer that one usually says before the proclamation of the Gospel.
In the meantime the Subdeacon of the Greek Rite waits before the stairs of the altar, in order to join the Deacon. The Deacon, having said the prayer, takes the Gospel Book, descends from the altar, genuflects to the Cross together with the Subdeacon and, accompanied by a Pontifical Master of Ceremonies, both go to the steps leading up to the papal throne. All remain kneeling on the floor before the steps while the Deacon asks for the blessing of the Supreme Pontiff.
Then all rise, genuflect to the Holy Father, and go by the shortest route to the lectern. The Subdeacon places himself at the back of the lectern, and the Deacon at the front of the lectern, opening thereon the Gospel Book.
In the meantime, the second Assisting Cardinal Deacon takes the miter from the Pope, who then stands up and remains standing for the duration of the chanting of the Gospel.
The Cardinal Deacon who ministers takes off the miter, rises and remains standing before the faldstool.
The Deacon of the Greek Rite begins the chanting of the Gospel, and with the thurible handed to him by the Thurifer, incenses the Gospel Book. He hands back the thurible and continues the chant until the end. The Subdeacon, with the chanting of the Gospel complete and having said the words: Doxa soi, Kyrie, doxa soi, takes the Gospel Book, and positions himself to the left of the Apostolic Subdeacon.
The Greek Deacon, flanked by two Acolytes, returns to the Epistle side near the column of the altar. The Acolytes place the candelabra on the credence table. The Apostolic Subdeacon, the Greek Subdeacon (followed by the Thurifer with the thurible, together with a Pontifical Master of Ceremonies) move toward the throne, and one after the other, ascending the throne, without genuflecting, present the Sacred Text to the Supreme Pontiff, who meanwhile kisses it and repeats the words: Per evangelica dicta, etc.
Both Subdeacons descend from the throne, genuflect to the Supreme Pontiff, and return to the altar. Having made a genuflection near the steps, each one hands over his respective Gospel Book to the Cleric of the Pontifical Chapel. The Apostolic Subdeacon positions himself near the Cardinal Deacon who is ministering; the Greek Subdeacon joins the Greek Deacon near the column of the altar, on the Epistle side.
The Assisting Cardinal Bishop, guided by the Master of Ceremonies, after the Pope has kissed the Sacred Text of the Gospels in Latin and in Greek, descends onto a step, and, having received the thurible from the Thurifer, incenses the Supreme Pontiff with a triple swing, returning the thurible to the Voting Member of the Signatura who, having genuflected to the Pope and the altar, gives it to the Acolyte of the Pontifical Chapel. (Giambattista Maria Menghini, Le Solenni Ceremonie della Messa Pontificale Celebrata dal Sommo Pontefice, ed. Desclée Lefebvre & c., edit. Pontifici, Roma 1904, cap. IV.§ 3)
In conclusion, without any pretense of having treated this topic in an exhaustive manner, one can hold that the present practice of chanting the Gospel in Greek during the Liturgia Verbi, as well as that of the diptychs of the Anaphora, has solid historical and theological foundations reminding one of the interdependent relationship between the lex credendi and the lex orandi in the Christian Liturgy. Besides, this practice of chanting the Gospel in both Latin and Greek is always a manifestation of the sole Catholic Church, even when the Liturgy is celebrated in a particular community. The Roman Liturgy, specifically, manifests the Catholic ecclesiology which recognizes the Bishop of Rome as the universal pastor.