The Holy Rule
How Many Psalms Are to Be Sung at These Hours
We have now arranged the order of the psalmody for the night and the morning office; let us next arrange for the succeeding Hours. At the first Hour let three psalms be said separately, and not under one Gloria. Let the hymn for the same Hour be said after the verse Deus, in adjutorium (Ps 69:2), before the psalms are begun. Then, after the completion of three psalms, let one lesson be said, a verse, the Kyrie eleison, and the collects.
At the third, the sixth, and the ninth Hours, the prayer will be said in the same order; namely, the verse, the hymn proper to each Hour, the three psalms, the lesson, the verse, the Kyrie eleison, and the collects. If the brotherhood is large, let these Hours be sung with antiphons; but if small, let them be said without a break.
Let the office of Vespers be ended with four psalms and antiphons; after these psalms a lesson is to be recited, next a responsory, the Ambrosian hymn, a verse, the canticle from the Gospel, the litany, the Lord's Prayer, and the collects.
Let Complin end with the saying of three psalms, which are to be said straight on without an antiphon, and after these the hymn for the same Hour, one lesson, the verse, Kyrie eleison, the blessing, and the collects.