Building upon the work of Ambrose, Sedulius and notably Prudentius, their own countryman; adapting ancient traditions of congregational worship and monastic usage, the liturgists of the seventh century must have collated for the use of the clergy approximately sixty-five hymns from sources originating prior to their own day. These ancient hymns form the nucleus of the Mozarabic Hymnal, the earliest manuscript of which dates from the tenth century. They reveal interrelations between the Spanish and Gallican churches and they indicate a continuity of hymn singing from primitive congregational usage like the Ambrosian to the seventh century revival and extension of non-scriptural hymns.[14] (See Illustrative Hymns, V. _Alleluia piis edite laudibus_, “Sing alleluia forth in duteous praise.”) III. Celtic Hymns The Celtic inhabitants of the British Isles from the period of the introduction of Christianity maintained individual features of liturgy and organization, especially in their monastic groups. The contemporary Saxon Church of the seventh century, however, had been drawn into the Roman sphere of influence by Gregory the Great who was also in touch with Celtic leadership. The ancient record of the interchange of hymns written respectively by St. Columba of Iona and by Gregory preserves more than a report incapable of proof.[15] It points to reciprocal interest in the evolving hymnology of the sixth and seventh centuries in Celtic and continental regions. The so-called Bangor Antiphonary of the seventh century is the earliest manuscript containing hymns, twelve in number.[16] Its contents are otherwise miscellaneous, including a list of the abbots of Bangor. Hilary’s supposed hymn from this collection, _Hymnum dicat turba fratrum_, has already been cited. An ancient communion hymn, _Sancti venite Christi corpus sumite_, “Draw nigh and take the body of the Lord,” is included and _Mediae noctis tempus est_, “It is the midnight hour,” an office hymn common to the hymnals of Spain and Gaul. Among other important sources is the Irish _Liber hymnorum_, preserved in an eleventh century manuscript of Dublin which contains Columba’s hymn, _Altus prosator_, “Ancient of days,” honoring God the creator, and the _Lorica_ or _Breastplate Hymn_ of St. Gildas (6th C.), _Suffragare trinitatis unitas, unitatis miserere trinitas_, “Grant me thy favor, Three in One, have mercy on me, One in Three.”[17]