Small sqaure miniature of Luke writing as the ox watches.

A book of hours is a type of devotional text that was popular in the Middle Ages, particularly in the late medieval period. It is a type of prayer book that contains a collection of prayers and devotional texts that were meant to be read at specific times of the day, known as the "hours." These texts were usually written in Latin and were intended for personal use by laypeople, although some were also used by monks and other religious figures. The book of hours typically included a calendar of feast days, psalms, and other prayers, as well as illustrations and decorations.

In artistic depictions, St. Luke is often shown holding an ox or with an ox nearby, as a symbol of his association with the Gospel of Luke and his devotion to Jesus and the Holy Family. The image of St. Luke with an ox is a reminder of the importance of sacrifice, devotion, and compassion in the Christian life.