The psalter (Book of Psalms), which had always been a part of Jewish worship and personal prayer, was one of the key books of the Bible for Christian clergy, monks and lay people in the middle ages. It was used as a hymnal in church services and in the daily prayer of the monks. Parts of the mass that are sung are often based upon psalm verses. It was read as a personal prayerbook, many of the psalms probably recited from memory. Theologians studied and commented upon it. Most medieval psalters have calendars, to help the user organise daily prayer by reminding them which saint's day it was, and special prayers of appeal to God and the saints (litany). A psalter's original place of use can sometimes be deduced from the saints named in the calendar and litany because a monastery, church or town will have its favourites. The names in this psalter point to the Benedictine abbey at Hyde. In the middle ages, psalters were divided into sections. The sections varied according to the psalter's origins and use. This one has the eight-fold or liturgical division. It accommodated the weekly round of prayers recited by the monks: one section for each day of the week plus one for evening prayers (vespers). The beginning of each section would be marked by having its first letter written large and decorated more than other letters in the manuscript. The third division begins with the Psalm 38 / 39 ("I said, 'I will watch my ways'"), seen here with its rich decoration of vines and a border around the page. Just above the large letter D, the words "Pater noster" ("Our Father") prompt recitation of the Lord's prayer at the end of the preceding psalm.