Purgatory refers to the papal doctrine that after death the souls of Christians go to a state of existence between Heaven and Hell called purgatory,1 where they undergo purification (or purging) “so as to achieve the holiness necessary to enter the joy of heaven”.2 The concept gradually developed over the first millennium,3 and then the medieval Western Church formulated the doctrine of Purgatory “especially at the Councils of Florence  and Trent .”2
The first reference claimed for this doctrine is the account in 2 Maccabees ch. 12 of the occasion (c. 161 BC) when Judas Maccabeus discovered that some of the Jewish soldiers whom he commanded had died in battle while wearing pagan amulets “sacred to the idols of Jamnia” (v. 40). Ch. 12 continues:
Written in Koinē Greek, 2 Maccabees is an apocryphal book, meaning that it was never part of the canon of Jewish Scriptures (that we call the Old Testament), because the Hebrew rabbis (teachers) did not consider it (or the other Maccabees books 1, 3, and 4) to be divinely inspired—and evidently, neither did its author.5 Hebrew scholar E.J. Young writes about the Apocrypha in general:
2 Maccabees focuses on the Maccabean revolt against Antiochus IV Epiphanes (Greek King of the Seleucid Empire; the sobriquet ‘Epiphanes’ had the blasphemous meaning of ‘[God] manifest [in Antiochus]) and concludes with the defeat of the Syrian General Nicanor. It also records attempts by various Gentiles to steal treasure from the temple in Jerusalem, and the battles fought by Judas Maccabeus to prevent this—in the second century after Malachi and before the birth of Christ. It contains no “Thus says the Lord …”, and God did not stipulate the payment mentioned. The latter thus appears to have been a pecuniary incentive to induce the Jerusalem priests to do what the Mosaic Law did not require or allow them to do, namely offer sacrifices for the dead.
Whether anything happened in Jerusalem is not recorded. However, many of the Jerusalem priests were Sadducees (including, on occasion, the high priest (i.e. ‘the CEO’, cf. Acts 5:17). The Sadducees were strict literalists with respect to the Old Testament Law and so did not believe in the resurrection of the dead or in any afterlife, for the reason that these are not mentioned by Moses in the Pentateuch, and hence the priests were hugely unlikely to have carried out the request. For this same reason, the Sadducees rejected the oral traditions of the Pharisees.
Interestingly, in Matthew 22:23–34, Jesus first rebuked them for not accepting the rest of Scripture, then proved them wrong (about the resurrection) with an argument from the books they did accept, which He affirmed as “what was said to you by God”!
Likewise, the claim that 1 Corinthians 3:10–15 refers to purgatory is made only by changing Paul’s focus from loss of reward for works, which is clearly what Paul is talking about, to punishment of souls for sin.
An indulgence is a letter authorized by the pope, to lessen the time people spend in purgatory.7 As the Bible does not mention the concepts of purgatory or of indulgences,8 the medieval Latin Church in the West developed a doctrine of “an infinite treasury” of “the superabundant merits of Christ and of the saints”, from which “satisfaction can be applied to others”,9 and since 1967 “the prayers and good works of the Virgin Mary”.10
However, sin is not acts of greater or lesser ‘deficiency in perfection’, but it is the desire of man to be totally free from the authority of God. One result of the disobedience to God of Adam and Eve (Genesis ch. 3) was that we have all been born with a sinful nature which expresses itself in our own deliberate rebellion against a holy God. Thus, because the whole human race is under God’s condemnation, we cannot initiate reconciliation. It must come from God. (See Dawkins’s dilemma: how God forgives sins.)
The good news is that God has done just that. Jesus Christ, the sinless Son of God, died on the Cross as our substitute to fully pay the just penalty for our sin (1 Peter 2:24; 3:18). The Bible says: “God … loved us and sent His Son to be the propitiation for our sins” (1 John 4:10). The Greek word translated “propitiation” in the KJV, NASB and ESV, and “expiation” in the RSV, is rendered “atoning sacrifice” in the NIV. It means that when the Lord Jesus died on the Cross, He was the means whereby the cost of our reconciliation with God was fully met (expiated), and God’s wrath upon us because of our sin was turned away (propitiated). See Good News.
The Apostle Paul tells believers to rejoice because we have been fully reconciled to God by Christ’s death (Romans 5:10–11; 2 Corinthians 5:18–20). And he wrote: “There is therefore now no condemnation for those who are in Christ Jesus” (Romans 8:1). On the cross, Jesus said to the penitent thief: “Today you will be with me in paradise” (Luke 23:43).
So, concerning people who have repented of their sins (and hence been forgiven by God, cf. 1 John 1:9), if they should still need to pay a sin-debt to God after death, this would mean that Christ’s substitutionary death on the cross was insufficient to pay the full penalty for their sins. If there was any other way to peace with God, other than through faith in Christ alone, then Jesus died needlessly (cf. Galatians 2:21).