Each of us has a duty to pray for our beloved family who have died; for those who taught us the faith- particularly those who taught by living the faith sanctified. Who by their shining example, their fervency, courage or compassion and service to the Gospel inspired us to be better Christians. That light perpetual would increasingly dawn upon them, in the place they have gone until the Last Day and the Resurrection of the Dead.
There is a Mexican saying that we die three deaths: the first when our bodies die, the second when our bodies are lowered into the earth out of sight, and the third when our loved ones forget us. Catholics forestall that last death by seeing the faithful dead as members of the Church, alive in Christ, and by praying for them — and asking their prayers for us — always. Cardinal Wiseman wrote in his Lecture XI:
Sweet is the consolation of the dying man, who, conscious of imperfection, believes that there are others to make intercession for him, when his own time for merit has expired; soothing to the afflicted survivors the thought that they possess powerful means of relieving their friend. In the first moments of grief, this sentiment will often overpower religious prejudice, cast down the unbeliever on his knees beside the remains of his friend and snatch from him an unconscious prayer for rest; it is an impulse of nature which for the moment, aided by the analogies of revealed truth, seizes at once upon this consoling belief. But it is only a flitting and melancholy light, while the Catholic feeling, cheering though with solemn dimness, resembles the unfailing lamp, which the piety of the ancients is said to have hung before the sepulchres of their dead.
Though we should daily pray for the dead in Purgatory, above all for our ancestors, today is especially set aside for hanging that “unfailing lamp before the sepulchres of our dead” as we are told to do by Sacred Scripture:
II Machabees 12: 43-46
And making a gathering, [Judas] sent twelve thousand drachms of silver to Jerusalem for sacrifice to be offered for the sins of the dead, thinking well and religiously concerning the resurrection, (For if he had not hoped that they that were slain should rise again, it would have seemed superfluous and vain to pray for the dead,) And because he considered that they who had fallen asleep with godliness, had great grace laid up for them. It is therefore a holy and wholesome thought to pray for the dead, that they may be loosed from sins.
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The Ostende Blog - Fr Christopher Young 