Rosary: Why Ten Hail Marys?

Q: Why is the rosary divided into groups of ten Hail Marys?

A: The ten Hail Marys are part of the evolution of the rosary. It was custom in the monastic tradition of the Middle Ages to say frequently the Psalter, i.e. 150 psalms of the Old Testament. Lay members of the order said in place of the psalms the Our Father (Pater). The 150 psalms/paters were subdivided in groups of fifty. During the twelfth-thirteen centuries, the Hail Mary was added. The next step was the Marian Psalter, i.e. 150 Hail Marys (without the Our Father). In order to avoid empty and mechanical recitation the Psalter was reduced to fifty Hail Marys called rosary (Rosarium), promoted by the Cistercians. The Dominican tradition consolidated the combination of Hail Marys and events of Jesus' life added to each Hail Mary. Over time fifteen mysteries (events of Jesus' life) were retained and combined with the Hail Marys for each one of the mysteries. Independently from this historical reason, there is a symbolic reason. Ten has the meaning of totality and unity, meaning that each one of Christ's mysteries is part of his total person and work and expresses its unity and totality, as well as its thorough contemplation by the person who says this decade of the rosary.