In the prayer and set of fundamental beliefs which we call “Apostles Creed,” a mention is made of the Communion of Saints. This means that the faithful on earth, the blessed in heaven, and the souls in purgatory are united in one Mystical Body with Christ as the head.
Those in heaven compose the Church Triumphant; those on earth, the Church Militant; and those in purgatory, the Church Suffering. All of them make one family and share the spiritual treasures of the Church. By prayers they help one another.
The Faithful on earth can relieve the sufferings of the souls in purgatory by prayer, fasting and other good works. The bible says in 2 Mac 12:46:
“It is a holy and wholesome thought to pray for the dead that they may loosed from their sins.”
St. Augustine says: “Prayer is the key by which we open the gates of heaven to the suffering souls.” At every Mass there is always a point for remembering the faithful departed.
The souls in purgatory suffer from a great longing to be united to God and from other great pains. They are yet deprived of the Beatific Vision and therefore need the help of those who can. We should pray for the poor souls. God does not regard so much the length of the prayer as the love in the heart of the one who prays. This short novena has been composed along that line: LOVE.
(transcribed from the Prologue of the Novena of Prayers for the Poor Souls)