18. The Order for Reciting the Psalms
First of all, this verse should be said with the doxology:
O God, come to my assistance;
O Lord, make haste to help me. (Ps 70:2)
Then comes the hymn for each hour.
2 At Prime on Sunday, recite four sections of Psalm 119. 3 At the other hours, that is, Terce, Sext, and None, three sections of the above-mentioned Psalm 119 are said.
4 Then at Prime on Monday let three psalms be recited, that is, Psalms 1, 2, and 3.
5 And so let three psalms be recited at Prime each day until Sunday, one after another through Psalm 20, with Psalm 9 in the Latin and Psalm 18 divided in two.
6 In this way, Vigils on Sunday will always begin with Psalm 21.
7 At Terce, Sext, and None on Monday, the nine remaining sections of Psalm 119 should be recited, three at each hour. 8 With Psalm 119 completed on these two days, that is, on Sunday and Monday, 9 the nine psalms from Psalms 120 to 128 should be sung at Terce, Sext, and None on Tuesday, three at each hour.
10 These psalms are always repeated at the same hours every day until Sunday, as also the arrangement of the hymns, readings, and verses, which remains the same for all these days. 11 And so Sunday will always begin with Psalm 119.
12 Now for Vespers each day, four psalms should be sung. 13 They should begin with Psalm 110 and go to Psalm 147, 14 except for those set apart for other hours, that is, Psalms 118 through 128 and Psalms 134 and 143. 15 All the rest should be recited at Vespers. 16 Since there are three psalms too few, those described above that are longer should be divided, that is, Psalms 139, 144, and 145. 17 But Psalm 117, since it is short, may be joined to Psalm 116.
18 With the order of the psalms for Vespers now arranged, let the rest be carried out, that is, the reading, responsory, hymn, verse, and canticle as we have determined above.
19 At Compline, repeat the same psalms every day: that is, Psalms 4, 91, and 134.
20 With the order of the psalms for the day hours now set, let all the remaining psalms be divided equally for the seven night offices of Vigils. 21 In order to have twelve psalms for each night, those that are longer must, of course, be divided in two.
22 Certainly we would counsel anyone who perhaps finds this distribution of the psalms unsatisfactory to arrange whatever he judges better, 23 provided that he takes care in every case that the entire Psalter of one hundred and fifty psalms is sung each week, and that it always begins anew at the Night Office on Sunday.
24 For monks show themselves exceedingly lax in the service that they have vowed if, during the course of a week, they sing less than the entire Psalter with the usual canticles, 25 since we read that our holy fathers briskly accomplished in a single day what we lukewarm monks hope to achieve only in an entire week.