The Psalter, or Book of Psalms, contained a calendar and other devotional texts used in the Christian liturgy as well as for private devotions. All 150 psalms were recited each week, the majority at matins (morning prayers) and vespers (evening prayers). Along with the psalms, psalters usually contained a calendar of feast days and a collection of other religious songs and creeds.
This leaf is written in Gothic rotunda, which was easier and faster to write than Gothic textura. It is possible that the large initial “B” was meant to be completed with a religious image or fill work in the center. However, many manuscripts exist in which there is no fill work and the capital letters are outlined in red and blue with white areas that create geometric patterns as seen here.