Chapter 23 in Scot McKnight's book 'The Heaven Promise' is entitled "What About Purgatory? A Theory That Divides the Church."
Purgatory has been the subject of much dissension, especially between Protestants and Roman Catholics. It is quite likely equally misunderstood by large numbers on both sides. Scot gives it this definition:
"Purgatory refers to a state or period between death and the final Heaven where, it is alleged by some theologians and ministers, those who are in Christ will be purged of their sins... There are two reasons given: (1) to stand in God's presence, we must be made worth of that presence; and (2) no one dies in a state of perfection. Therefore, something has to happen to make someone worthy of God's presence. At this point Protestants and Catholics take different paths. The Protestants agree with the two points but believe God in his grace will instantaneously make humans fit for God's presence by an act of glorification. Roman Catholics, emphasizing more a belief in human will, believe humans will cooperate with God as God makes that person fit for that glorious presence. Hence, either one believes in glorification by a sudden act of God's grace, or one believes in purgatory."
Scot suggests there are two possible texts relevant to a discussion of purgatory. One is in what is referred to as the Old Testament Apocrypha, in 2 Maccabees 12:32-45. This is not printed as a part of the Protestant Bible. It refers to the custom of praying for the souls of the dead that they might join the final resurrection.
A second text is 1 Corinthians 3:11-15, where Paul seems to be saying that either at death or after death the things we have done in our earthly lives will be tested by fire. What survives the test is eternal, and what doesn't survive will be burned with fire. McKnight believes this refers to works, and not people, being tested.
In conclusion, Scot says he finds no biblical basis for purgatory in either of these texts. He says, "In the Bible, the fire that purges is an act of God and not something in which we participate... There is a real danger in the doctrine of purgatory in minimizing the completeness of God's work for us in Christ and the importance of grace."
So... there ya go.