A Novena for the Holy Souls

The Benedictine abbot Odilo of Cluny established a day of prayer for all the faithful departed at his monastery in 998, setting it for the day after the feast of All Saints; the custom spread from Cluny to the rest of the Western Church over the following two centuries.

The scriptural basis usually given for praying for the dead is 2 Maccabees 12:43-46, where Judas Maccabeus takes up a collection after a battle and sends it to Jerusalem for a sin offering on behalf of soldiers found to have died in idolatry.

The doctrine that souls in purgatory can be helped by the prayers of the living was defined at the Council of Florence in 1439 and reaffirmed at the Council of Trent in 1563; John Henry Newman's 1865 poem The Dream of Gerontius, later set to music by Elgar, gives one of the best-known literary pictures of a soul's passage through it.

In 1915, during the mass casualties of the First World War, Pope Benedict XV granted every priest in the world permission to offer three Masses on All Souls' Day instead of the usual one, a privilege that remains in effect.

The Church attaches a plenary indulgence, applicable only to the dead, to a visit made to a cemetery on any day from 1 to 8 November while praying for the departed, a practice formalized well after the custom of visiting graves at this time of year had already existed for centuries.

Roman catacomb inscriptions from as early as the second century already ask for prayers on behalf of the buried, short phrases scratched by hand such as in pace and vivas in Deo, may you live in God.

The Office of the Dead, a set of psalms and readings said or sung on behalf of a deceased person, was a fixture of medieval monastic life and, through the Books of Hours, one of the most widely copied texts of the later Middle Ages.

The Ars moriendi, or art of dying, was a genre of devotional handbook that spread across Europe from the early fifteenth century, teaching the dying and those attending them how to prepare a soul for its judgment.

The Catechism of the Catholic Church, published in 1992, restates the doctrine in a single paragraph, numbered 1032, citing both 2 Maccabees and the Church's ancient practice of praying, giving alms, and offering the Eucharistic sacrifice for the dead.