Four psalms are sung each day at Vespers, starting with Psalm 110 and ending with Psalm 147, omitting the psalms in this series already assigned to other hours, namely, Psalms 118 through 128, Psalm 134 and Psalm 143. All the remaining psalms are said at Vespers.Since this leaves three psalms too few, the longer ones in the series should be divided: that is Psalms 139, 144 and 145. And because Psalm 117 is short, it can be joined to Psalm 116. This is the order of psalms for Vespers; the rest is as arranged above: the reading, responsory, hymn, versicle and canticle.
In determining the order of the psalms for the prayer life of his community, Benedict grounds Prime, Terce, Sext and None, the Little Hours of the Divine Office, in the Wisdom Psalm, 119. Wisdom psalms were not liturgical hymns of lament or praise. They were meant to instruct the assembly in divine truths and were often built on the alphabet in order to make memorization easier. Modern educators write children's books or songs in the same way and for the same reason. Psalm 119, therefore, has 22 sections, with each of the eight verses of each section beginning with one of the letters of the Hebrew alphabet.
It is this longest of all psalms, with its theme of the trustworthiness of God's law, the richness of God's will for us, the excellence of God's loving design for us that Benedict wants us to learn and say daily and never forget.