Curiosities
Why 150 Hail Marys?
Mary's Psalter
The number 150 echoes the Book of Psalms. As monks prayed the 150 Psalms, lay people prayed 150 Hail Marys as 'the Psalter of the Blessed Virgin Mary'. The Psalter was traditionally divided into three sets of fifty, and so was the Rosary: the Joyful, Sorrowful and Glorious Mysteries, each a set of five decades. In Spanish, one such third is still called a tercio, and 'to pray a tercio' means to pray five decades.
A single set of fifty was called a 'chaplet', from the Old French chapelet, a little wreath or crown for the head. The ten Hail Marys between two Our Fathers are a 'decade'. When St. John Paul II added the Luminous Mysteries in 2002, the complete Rosary grew to twenty decades and two hundred Hail Marys. He noted that the traditional number came from the 150 Psalms, but judged that the new mysteries would deepen its Gospel character without altering its essential form.