This rite is to be found in the liturgical books of the order. The collection, composed of fifteen books, was made by the General Chapter of Cîteaux, most probably in 1134; they are now included in the Missal, Breviary, Ritual, and calendar, or Martyrology. When Pius V ordered the entire Church to conform to the Roman Missal and Breviary, he exempted the Cistercians from this law, because their rite had been more than 400 years in existence. Under Claude Vaussin, General of the Cistercians (in the middle of the seventeenth century), several reforms were made in the liturgical books of the order, and were approved by Alexander Vll, Clement IX, and Clement XIII. These approbations were confirmed by Pius IX on 7 Feb., 1871, for the Cistercians of the Common as well as for those of the Strict Observance. The Breviary is quite different from the Roman, as it follows exactly the prescriptions of the Rule of Saint Benedict, with a very few minor additions. Saint Benedict wished the entire Psalter recited each week; twelve psalms are to be said at Matins when there are but two Nocturns; when there is a third Nocturn, it is to be composed of three divisions of a canticle, there being in this latter case always twelve lessons. Three psalms or divisions of psalms are appointed for Prime, the Little Hours, and Compline (in this latter hour the “Nunc dimittis” is never said), and always four psalms for Vespers. Many minor divisions and directions are given in Saint Benedict’s Rule.
In the old missal before the reform of Claude Vaussin, there were wide divergences between the Cistercian and Roman rites. The psalm “Judica” was not said, but in its stead was recited the “Veni Creator”; the “Indulgentiam” was followed by the “Pater” and “Ave”, and the “Oramus te Domine” was omitted in kissing the altar. After the “Pax Domini sit semper vobiscum”, the “Agnus Dei” was said thrice, and was followed immediately by “Hæc sacrosancta commixtio corporis”, said by the priest while placing the small fragment of the Sacred Host in the chalice; then the “Domine Jesu Christe, Fili Dei Vivi” was said, but the “Corpus Tuum” and “Quod ore sumpsimus” were omitted. The priest said the “Placeat” as now, and then “Meritis et precibus istorum et onmium sanctorum. Suorum misereatur nostri Omnipotens Dominus. Amen”, while kissing the altar; with the sign of the Cross the Mass was ended. Outside of some minor exceptions in the wording and conclusions of various prayers, the other parts of the Mass were the same as in the Roman Rite. Also in some Masses of the year the ordo was different; for instance, on Palm Sunday the Passion was only said at the high Mass, at the other Masses a special gospel only being said. However, since the time of Claude Vaussin the differences from the Roman Mass are insignificant.
In the calendar there are relatively few feasts of saints or other modern feasts, as none were introduced except those especially prescribed by Rome for the Cistercian Order; this was done in order to adhere as closely as possible to the spirit of Saint Benedict in prescribing the weekly recitation of the Psalter. The divisions of the feasts are: major or minor feast of sermon; major or minor feast of two Masses; feast of twelve lessons and Mass; feast of three lessons and Mass; feast of commemoration and Mass; then merely a commemoration; and finally the feria.
The differences in the ritual are very small. As regards the last sacraments, Extreme Unction is given before the Holy Viaticum, and in Extreme Unction the word “Peccasti” is used instead of the “Deliquisti” in the Roman Ritual. In the Sacrament of Penance a shorter form of absolution may be used in ordinary confessions.