Used as a prayerbook as well as a book of hymns for church services, the psalter in the later middle ages was often produced with a calendar and additional prayers. Eventually it was combined with an abridged version of the breviary, the prayerbook used by monks, to form the special lay prayerbook, the book of hours. This psalter represents an important stage in this development as it took place in England. It is one of the earliest psalters to include the Hours of the Virgin, a special set of devotions taken from the breviary. Also it is the earliest of a line of richly decorated psalters which were probably made at Oxford, in the workshops by lay scribes and artists, an industry which grew out of book production for the university. Medieval psalters are given divisions according to four traditions. This psalter has the most recent, the tenfold, which was a combination of earlier traditions. Psalm 51 begins one of the divisions and as such is given a large historiated initial. The picture in it shows King Saul commanding one of his retinue, Doeg the Edomite, to behead the priests of Nob because they sided with David (1 Samuel 22). The subject was chosen because the psalm's title, below in red, explains that it is about Amalech, who has a role in the story. The priests are shown not as Jewish but as Christian monks.