Section — Bucceroni, Institutions of Moral Theology
II. Concerning Octaves
The Octaves of Easter, Pentecost, Epiphany, the Most Holy Body of Christ, the Nativity of the Lord, and Ascension are privileged; and concerning them, if sometimes the whole Office is not to be made, nevertheless a Commemoration is always made at Lauds, Mass, and Vespers. Their Office is recited entirely as on the Feast day, except those things which are assigned in their own places.
But in the Office both of a day within the Octave and of the Octave Day of any other Doubles of the first class, even of the Lord, the antiphons and psalms at all the Hours and the Verses of the Nocturns are to be said from the occurring day of the week; and the Lessons of the first Nocturn, unless proper ones are had, or, when Lessons from Scripture are lacking, must be taken from the Feast or from the Common, are said with their Responsories of the Time, as will be said below. But an Octave Day of this kind, even of the Lord, both in occurrence and in concurrence, yields to any Sunday.
But concerning the Octaves of Doubles of the second class of the universal Church, nothing is made except on the Octave Day, and indeed under simple rite: so that if on it some Double or Semidouble Office occurs, even one replaced or transferred, or a greater Feria or Vigil, only a Commemoration is made of an Octave Day of this kind according to the Rubrics. But occurring Simple Feasts are commemorated in the Office of the Octave Day, to which also the Office of St. Mary on Saturday yields, to be omitted in the case.
The same is observed concerning the Octaves of Doubles of the second class of some Diocese or particular Church, which likewise, unless they wish them to be entirely omitted, will have to be celebrated only on the Octave Day and under simple rite.
The Octaves of particular Feasts after the day of the Nativity of the Lord are no longer impeded.
The Lessons of the second and third Nocturns assigned up to now on individual days through the Octaves of Feasts of Double of the second class of the universal Church are to be inserted in the Roman Octavary; but not the Lessons of the first Nocturn, even if proper ones are had.