Christian practice reveals a third type of Hebrew influence, the liturgical, which brought about the use of the psalms in public worship, together with other elements familiar in the synagogue. At the close of a service of this kind, made up of prayers, readings, psalms and preaching, the eucharist was celebrated. Early writings, for example, the Apologia of Justin Martyr, 100?-165,[19] the Didache[20] and the Apostolic Constitutions,[21] testify to a somewhat fixed type of worship, which, varying in details, seems to foreshadow the liturgical models of the fourth century.

Briefly stated, the Didache, or Teaching of the Twelve Apostles, is a second century treatise, the second part of which includes a ritual of baptism, fasting and the eucharist.[22] A series of eucharistic prayers is here recorded, beginning, {Eucharistoumen soi, pater hemon},

We thank Thee, our Father,

offered at stages of the communion ritual where we approach the heart of Christian worship.[23] At this point, hymn and prayer origins merge. Many Christians of our own day, perhaps the majority, regard the true hymn as a prayer offered in direct address to God. Throughout the history of Christian hymns the two forms of worship have overlapped or been identical. Hymn and prayer were also associated in ancient cults, and the chorus of a Greek drama offers an illustration of the superb proportions which this act of worship may assume. Charles Stanley Phillips, who has recently translated anew the eucharistic prayer of the Didache, thinks of it as not a true hymn, but a source and model of hymnody.[24] Improvised eucharistic prayer was interrupted by congregational refrains which provided another opportunity for the evolution of hymns. As a matter of fact, in all ages, expressions of thanksgiving, attending the celebration of the eucharist, have inspired many of the finest hymns of the faith.

The Apostolic Constitutions is a manual in eight books, of ecclesiastical discipline, doctrine and worship, including the Didache.[25] Dating from the fourth or fifth century, more probably the fourth, it represents the practice of an earlier period well within the scope of this study and, in the opinion of Brightman, was compiled in Antioch or its neighborhood.[26] Since Greek was the prevailing language in the Christian world of that day, it became the liturgical language of early Christianity for the first three centuries. Even in Rome and other large cities of Italy, Greek was used. In Italy, with these exceptions and in the western provinces, Latin was employed, finally superseding Greek as the official language of the Western Church.[27]

The following hymns appear in the seventh book of the Apostolic Constitutions:

A morning hymn, {Doxa en hypsistois theo}, Gloria in excelsis,

Glory to God in the highest;[28]

an evening hymn, {Aineite paides},

Ye children praise the Lord,[29]

which includes {Soi prepei ainos}, Te decet laus,

Praise becomes Thee,

and {Nyn apolyeis ton doulon sou}, Nunc dimittis,

Now lettest thou thy servant depart in peace;

and a prayer at dinner, {Eulogetos ei},

Thou art blessed, O Lord, who nourishest me from my youth.[30]

In the eighth book of the Apostolic Constitutions and also in the Liturgy of St. James we have the Tersanctus, {Hagios, hagios, hagios},

Holy, holy, holy.

In another part of the same Liturgy the Trisagion appears, {Ho trisagios hymnos,},

Holy God, holy mighty, holy immortal,
Have mercy upon us.[31]

An evening hymn, {Phos hilaron}, Joyful light, is mentioned by Basil in the fourth century as very old. It was sung at vespers in the Eastern Church:[32]

O gladsome light, O grace
Of God the Father's face.[33]

Among ancient liturgical hymns the Te deum should be mentioned. It is attributed to Nicetas, Bishop of Remesiana in Dacia, and dated from the end of the fourth century. It appears to be a combination of three distinct parts. The first thirteen verses, or parts one and two, probably originated earlier than the fourth century and may have been inspired by Cyprian, Bishop of Carthage, 200-258, who wrote in terms almost identical with the phrases of this early section, used of prophets, apostles and martyrs.[34]

Biblical sources, especially the canticles, now appear as liturgical hymns, either in their original form or in an enlarged version.[35] The use of canticles, more particularly in their variations, is of supreme interest to the hymnologist, because it offers a theory of the origin of Christian hymnody apart from liturgical interpolations or from the psalms. Clement of Rome urged the Corinthians to unite in the spirit of praise as expressed in the seraphic chorus of Isaiah's vision,

Holy, holy, holy is the Lord of Hosts:
the whole earth is full of his glory,

associating it with the praise of the angelic ministrants, "ten thousand times ten thousand," beheld by Daniel (Dan.7:10). The same hymn had been heard in the apocalyptic mysteries of the Book of Revelation. Very early it was incorporated in the liturgy of the eucharist, continuing an ageless form of the praise of God from the old dispensation into the new.

The evolution of the Great Doxology from the words of the angelic song,

Glory to God in the highest,

to the Gloria in excelsis illustrates the expanding thought of the Church, corresponding to the growth of the Christian body within the culture of the Roman Empire. Again, the Gloria illustrates Hellenistic features of poetic style, bespeaking the oriental influences which had entered into Greek literature.[36] Note the repetition of the clauses,

We praise thee, we bless thee, we worship thee, we glorify thee, we give thanks to thee for thy great glory,

of the invocation,

O Lord God, heavenly King, God the Father almighty, O Lord, the only-begotten Son, Jesus Christ;
O Lord God, Lamb of God, Son of the Father,

of the relative clause,

That takest away the sins of the world, have mercy upon us. Thou that takest away the sins of the world, receive our prayer. Thou that sittest at the right hand of God the Father, have mercy upon us,

of the pronoun,

For thou only art holy; thou only art the Lord; thou only, O Christ, with the Holy Ghost, art most high in the glory of God the Father.

It is quite superfluous to analyze further the values of a poetic form which has helped to make the Gloria one of the truly magnificent Christian hymns of all ages.[37]

Postponing for the present a more detailed inquiry into stylistic origins, we may regard the group of liturgical hymns here presented as a source collection of the utmost importance. It reveals not only the continuity of the Old and New Testament hymnology but also the evolution of worship in song into the early Christian era. The fact that worship was chiefly liturgical in this period and hymns were therefore liturgical appears an inevitable conclusion.