Augustine Taught The Heresy of Purgatory and Prayers For The Dead
“That there should be some fire even after this life is not incredible, and it can be inquired into and either be discovered or left hidden whether some of the faithful may be saved, some more slowly and some more quickly in the greater or lesser degree in which they loved the good things that perish, through a certain purgatorial fire”
(Handbook on Faith, Hope, and Charity 18:69 [A.D. 421]).
“We read in the books of the Maccabees [2 Macc. 12:43] that sacrifice was offered for the dead. But even if it were found nowhere in the Old Testament writings, the authority of the Catholic Church which is clear on this point is of no small weight, where in the prayers of the priest poured forth to the Lord God at his altar the commendation of the dead has its place”
(The Care to be Had for the Dead 1:3) [A.D. 421]
“There is an ecclesiastical discipline, as the faithful know, when the names of the martyrs are read aloud in that place at the altar of God, where prayer is not offered for them. Prayer, however, is offered for other dead who are remembered. It is wrong to pray for a martyr, to whose prayers we ought ourselves be commended”
(Sermons 159:1) [A.D. 411]
“But by the prayers of the holy Church, and by the salvific sacrifice, and by the alms which are given for their spirits, there is no doubt that the dead are aided, that the Lord might deal more mercifully with them than their sins would deserve. The whole Church observes this practice which was handed down by the Fathers: that it prays for those who have died in the communion of the Body and Blood of Christ, when they are commemorated in their own place in the sacrifice itself; and the sacrifice is offered also in memory of them, on their behalf. If, then, works of mercy are celebrated for the sake of those who are being remembered, who would hesitate to recommend them, on whose behalf prayers to God are not offered in vain? It is not at all to be doubted that such prayers are of profit to the dead; but for such of them as lived before their death in a way that makes it possible for these things to be useful to them after death”.
(Sermons 172:2) [A.D. 411]
“Temporal punishments are suffered by some in this life only, by some after death, by some both here and hereafter, but all of them before that last and strictest judgment. But not all who suffer temporal punishments after death will come to eternal punishments, which are to follow after that judgment”.
(The City of God 21:13) [A.D. 419]
“The time which interposes between the death of a man and the final resurrection holds souls in hidden retreats, accordingly as each is deserving of rest or of hardship, in view of what it merited when it was living in the flesh. Nor can it be denied that the souls of the dead find relief through the piety of their friends and relatives who are still alive, when the Sacrifice of the Mediator [Mass] is offered for them, or when alms are given in the Church. But these things are of profit to those who, when they were alive, merited that they might afterward be able to be helped by these things. There is a certain manner of living, neither so good that there is no need of these helps after death, nor yet so wicked that these helps are of no avail after death”.
(The City of God 29:109) [A.D. 419]