"Hmm. Anyone know when this doctrine first showed up, or was made official by the church? It isn't found in Scripture."
Like heck it isn't! (Heck is for people who don't believe in Gosh.)
The word purgatory is a Latin word, meaning cleansing. Like the Latin word "Trinity," the WORD doesn't exist in the bible, but the concept does.
In fact, at Worms, Martin Luther lost a debate wherein it was conclusively proven that the Books of Hebrews, the letters of Peter, Revelations, and Maccabees all refer to atonement. Luther responses by claiming that these books were not scriptural. Other Protestants movements couldn't break the Tradition of including Hebrews and Revelations; they were too well known. Maccabees, being a more obscure Old Testament book, was easier to cover up, especially since the Jews had rejected the book in AD 70 -- after Christ -- because it explicitly foretold the Resurrection.
The key thing is that Christ's atonement saves our souls from ETERNAL condemnation. That doesn't mean we don't have to live with the TEMPORAL suffering caused by our mistakes. If a man is promiscuously homosexual and catches AIDS, being saved saves his ETERNAL soul, but he still suffers the TEMPORAL consequence of the disease he has caught. If a teenage loses his leg pulling stunts on a railroad track, and is saved, it is his ETERNAL soul that is saved. He still deals with the TEMPORAL consequence of having only one leg. And no miracle worker around is going to make him grow another leg.
Likewise, when we sin, WE alienate OURSELVES from God. We know nothing impure can enter Heaven, and our shame holds us back, until we accept total forgiveness. Saints are those who are purified on this earth, and so for some time on earth experience a perfected will. Protestants insist that all who are "saved" are saints. Is that so? Can you command mountains to toss themselves into the sea? How many lepers have you healed? Are you totally without sin? Does your will confirm completely with God's? Even worse is the tendency for some brands of Protestants to establish that nothing they do can be a sin, because they still do it in spite of being saved.
So, let's see where the bible tells us of a place of suffering or incomplete beatific vision (complete spiritual intimacy with God):
Revelations depict saints and martyrs already in Heaven (such as 5:9-14). These are those who have already been made pure by the blood of the lamb (7:5-17). Those who are in Hades are resurrected only later, and they are judged according to their works (20:11-15). Are all the judged condemned? No! There exists a book of life (20:12), and only those who are not found in the book of life are condemned (20:15). THe "servants and saints" are rewarded, while the destroyers are destroyed (11:19). On that day, the Earth will be destroyed by fire. Paul writes that many will survive, but their works will be destroyed. They will survive, as one who passes through fire (1 Corinthians 3:13-15).
In 2 Maccabees, the Jews were promised that the faithful would not die in battle, but many who fought valiantly for the Lord did die. The comrades of the dead found that the dead had worn amulets, idolatry. They were so aggrieved for those they loved, that they atoned for the dead by offering up the loot from the war to the temple. "Thus he made atonement for the dead" (12:38-46). It was with this loot that the Temple was rededicated on December 25, a feast attended by Jesus (John 10:22). And when Jesus died, the Maccabees' altar and curtain were destroyed (Matthew 27:50-52).
There was no word for purgatory in the bible, simply because the Jews would not have comprehended such a word. They knew only of the grave (Sheol, translated to Hades for the Greeks). But was Hades necessarily a permanent place? Did only the eternally condemned suffer any time in Hades? Not at all! In fact, we are told that the gates of Hades will not withstand the church (Matthew 16:18). (This is unfortunately confusingly transalted as "prevail." How do gates "prevail?" The word means to "resist being thrown down.") The GATES to Hades, which enclose it, will be torn down by the church! It's a prison raid! It's right after Jesus tells Peter the church will raid the prison of Hades that Peter is given the KEYS to Heaven! (16:19) (There are other, very significant meanings to the symbolism.)
Also, the notion of a PRISON as a TEMPORAL dwelling in Hades occurs many times in the New Testament.
Mark