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: 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.
The order of the Vesper Psalms being thus settled, let the rest of the Hour - lesson, responsory, hymn, verse and canticle - be carried out as we prescribed above.
For those monastics show themselves too lazy in the service to which they are vowed, who chant less than the Psalter with the customary canticles in the course of a week, whereas we read that our holy Fathers strenuously fulfilled that task in a single day.
[2] However, after the Second Vatican Council and the promulgation of the new Liturgy of the Hours, each monastery has the right to make his own monastic liturgy under the guidelines of the Thesaurus Liturgiae Horarum Monasticae (1977) which allows the usage of a different psalter order than Saint Benedict's or the retention of the canonical hour of Prime which was suppressed by Sacrosanctum Concilium.