6 We are moved to this both by the pious desires of Catholics to whom We knowthat Our resolution will be especially grateful, and by the fearful tortureswhich the souls of the departed suffer, but We are also animated by the customof the Church, which, amidst the most joyous solemnities of the year, fails notto make a holy and salutary commemoration of the dead that they may be deliveredfrom their sins.
Source: Quod Anniversarius (Vatican.va)