Gloria Patri (the "shorter Doxology")

Glory be to the Father, and to the Son and to the Holy Spirit. As it was in the beginning, is now, and will be for ever. Amen

The doxology in the form in which we know it has been used since about the seventh century all over Western Christendom. The Fourth Synod of Toledo in 633 ordered this form (can. xv). A common medieval tradition, founded on a spurious letter of St. Jerome (in the Benedictine edition, Paris, 1706, V, 415) says that Pope Damasus (366-384) introduced the Gloria Patri at the end of psalms. Cassian (died c. 435) speaks of this as a special custom of the Western Church (De instit. coen., II, viii). The use of the shorter doxology in the Latin Church is this: the two parts are always said or sung as a verse with response. They occur always at the end of psalms (when several psalms are joined together as one, as the sixty-second and sixty-sixth and again the one hundred and forty-eighth, one hundred and forty-ninth and one hundred and fiftieth at Lauds, the Gloria Patri occurs once only at the end of the group; on the other hand each group of sixteen verses of the one hundred and eighteenth psalm in the day Hours has the Gloria) except on occasions of mourning. For this reason (since the shorter doxology, like the greater one, Gloria in Excelsis Deo, in naturally a joyful chant) it is left out on the last three days of Holy Week; in the Office for the Dead its place is taken by the verses: Requiem æternam, etc., and Et lux perpetua, etc. It also occurs after canticles, except that the Benedicite has its own doxology (Benedicamus Patrem . . . Benedictus es Domine, etc. -- the only alternative one left in the Roman Rite). In the Mass it occurs after three psalms, the "Judica me" at the beginning, the fragment of the Introit-Psalm, and the "Lavabo" (omitted in Passiontide, except on feasts, and at requiem Masses). The first part only occurs in the responsoria throughout the Office, with a variable answer (the second part of the first verse) instead of "Sicut erat," the whole doxology after the "Deus in adjutorium," and in the preces at Prime; and again, this time as one verse, at the endof the invitatorium at Matins. At all these places it is left outin the Office for the Dead and at the end of Holy Week. The Gloria Patri is also constantly used in extraliturgical services, such as the Rosary. It was a common custom in the Middle Ages for preachers to end sermons with it.In some countries, Germany especially, people make the sign ofthe cross at the first part of the doxology, considering it as chiefly a profession of faith.

[From the Catholic Encyclopedia]

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