Following the feast of All Saints, the Church celebrates the Solemnity of All Souls on November 2. This celebration remembers all the souls who have died and have not yet attained Heaven, who are still atoning for the sins in their lives. The faithful still living can help these souls reach heaven through prayers, especially with the offering of a Mass.
The Catholic Church has always prayed for the dead, but the feast of All Souls is an annual recognition of this tradition. As early as the sixth century, Benedictine monasteries held commemoration ceremonies for their deceased members. In the 11th century, St. Odilo of Cluny chose the day after All Saints’ Day in his decree that Masses should be offered for the dead, and alms given to the poor. This custom spread to other monasteries and eventually to the Church around the world.