Today is the Feast of All Souls, when Christians traditionally pray for the dead, that they may have eternal rest.
The early Church, in both its literary and archeological remains, testifies to belief in purgatory. Many Christians commissioned gravestones with epitaphs begging prayers for their souls. The apocrypha sketch out the doctrine, and the Fathers expound it. The existence of purgatory is implicit in both the Old Testament and the New (including the Gospels). The early Church kept many graveside traditions that, in effect, made a habit of prayer for the dead. It was customary to mark the anniversary of a dead person’s passing (three days, one week, one year) with the celebration of the Mass. In the fourth century, St. Monica urged her priest-son Augustine to remember her soul in prayer when he said Mass. And, like a good boy, he did. “If we had no care for the dead,” Augustine said, “we would not be in the habit of praying for them.” Augustine held that there are “temporary punishments after death.” There is remedial pain as the soul undergoes its purification and preparation for heaven. St. Gregory the Great emphasized that this doctrine was not optional.
The earliest records in the paper trail are not to be missed, for they’re the most poetic. And you’ll find a sampling online here.
The best book on the subject is, without a doubt, Purgatory, by Michael Taylor, S.J. It presents the scriptural, patristic, and theological evidence in an accessible readable form. It’s a friendly treatment, good for handing to a skeptical friend.
“He also took up a collection, man by man, to the amount of two thousand drachmas of silver, and sent it to Jerusalem to provide for a sin offering. In doing this he acted very well and honorably, taking account of the resurrection. For if he were not expecting that those who had fallen would rise again, it would have been superfluous and foolish to pray for the dead. But if he was looking to the splendid reward that is laid up for those who fall asleep in godliness, it was a holy and pious thought. Therefore he made atonement for the dead, that they might be delivered from their sin” (2 Maccabees 12:43-45). “It is a holy and wholesome thought to pray for the dead that they may be loosed from their sins” (2 Maccabees 12:46, Vulgate).