The Benedictine Rite is the particular form of Mass and Liturgy celebrated by the Benedictine Order, as based on the writings of St. Benedict on the topic. Mass The Benedictine Order never had a rite of its own celebrating Mass. Since the reform of Pope Pius V (see Quo primum), it always uses the Roman Rite of Mass; earlier, its monks often used local rites, as did those who served the cathedral of Durham. Liturgy of the Hours However, the Order has always had its own form of celebrating the Liturgy of the Hours, in accordance with what was called the Breviarium Monasticum. The founder, St. Benedict devotes thirteen chapters (8-20) of his rule to regulating the canonical hours for his monks (and nuns). Chapter 18 specifies how they should pray the psalms: In What Order the Psalms Are to Be Said Let this verse be said: "Incline unto my aid, O God; O Lord, make haste to help me," and the "Glory be to the Father" then the hymn proper to each Hour. Then at Prime on Sunday four sections of Psalm 118 are to be said; and at each of the remaining Hours, that is Terce, Sext and None, three sections of the same Psalm 118. At Prime on Monday let three Psalms be said, namely Psalms 1, 2 and 6. And so each day at Prime until Sunday let three Psalms be said in numerical order, to Psalm 19, but with Psalms 9 and 17 each divided into two parts. Thus it comes about that the Night Office on Sunday always begins with Psalm 20. At Terce, Sext and None on Monday let the nine remaining sections of Psalm 118 be said, three at each of these Hours. Psalm 118 having been completed, therefore, on two days, Sunday and Monday, let the nine Psalms from Psalm 119 to Psalm 127 be said at Terce, Sext and None, three at each Hour, beginning with Tuesday. And let these same Psalms be repeated every day until Sunday at the same Hours, while the arrangement of hymns, lessons and versesis kept the same on all days; and thus Prime on Sunday will always begin with Psalm 118. Vespers are to be sung with four Psalms every day. These shall begin with Psalm 109 and go on to Psalm 147, omitting those which are set apart for other Hours; that is