The fifteenth Sunday after Pentecost is of semi-double rite and its liturgical colour is white. This year it is the third Sunday of September and also Sunday within the Octave of the Nativity of the BVM.
Vespers yesterday afternoon were 'from the chapter' of the Sunday. The antiphons and psalms were those from the feast of the Nativity of the Blessed Virgin, Nativitas gloriosae Virginis Mariae etc with Pss. 109, 112, 121, 126 & 147. The chapter was O Altitudo and the Office hymn O lux beata Trinitas. Hymns of Iambic metre were sung with the Doxology and melody of the Incarnation, Gloria tibi Domine etc throughout the Octave. The antiphon on the Magnificat was Ne reminiscaris for the Saturday before the third Sunday of September. After the collect of the Sunday a commemoration was sung of the Octave of the Nativity of the BVM. At Compline the Dominical preces were omitted because of the Octave.
At Mattins the invitatory is Adoremus Dominum and the Office hymn Nocte surgentes. In the first nocturn (Pss. 1, 2, 3, 6, 7, 8, 9, 10, 11, 12, 13 & 14) are sung. The lessons are the Incipit of the Book of Tobias. The first lesson continues with what is now the beginning of the second lesson Deinique, cum irent... to ...ministraret omnem decimationem. The second lesson begins Haec et his similia.. to ... salutis dabat eis, what is the end of the third lesson in the modern editions. The third lesson, absent from modern editions, begins Cum autem venisset... and continues until ...solicitus exhibebat. (vv. 16 - 20). In the second nocturn (Pss. 15, 16 & 17) the lessons are from a sermon of St. Leo. The sixth lesson is slightly longer than that found in the modern editions, the seventh and eighth lessons are the same. In the third nocturn (Pss. 18, 19 & 20) the homily is from St. Augustine on St. Luke's Gospel. The entire seventh lesson is absent from modern editions: Miracula Domini nostri ... quam suscitare iterum moriturum. The eighth lesson is significantly longer than that found in modern editions. The ninth lesson is the same as that found in the modern books. The Te Deum is sung.
At Lauds the Sunday psalms (Pss. 92, 99, 62-66, Benedicite 148-49-150) are sung. After the collect of the Sunday a commemoration of the Octave is sung. The Suffrages are not sung because of the Octave.
At Prime (Pss. 53, 117, 118i & 118ii) Quicumque is sung but the Dominical preces are omitted due to the Octave. In the short responsory the verse Qui natus es is sung. At the Hours the hymns are sung with the Doxology and melody of the Incarnation.
Mass is sung after Terce. The Gloria is sung, the second collect is of the Octave. There is no third collect. The Credo is sung and the preface is of the BVM.
Vespers are of the Sunday (Pss. 109, 110, 111, 112 & 113). After the collect of the Sunday a commemoration is sung of the Octave. The Suffrages are omitted as are the Dominical preces at Compline.