'This seems so simple. Its common sense. Scripture is very clear when it says, “But nothing unclean shall enter [heaven]” (Rev. 21:27). Hab. 1:13 says, “You [God]… are of purer eyes than to behold evil and cannot look on wrong…”
How many of us will be perfectly sanctified at the time of our deaths? How many unconfessed venial sins (thoughts/words/deeds) will we have at the time of our death? I dare say most of us will be in need of further purification in order to enter the gates of heaven after we die, if, please God, we die in a state of grace.
In light of this, the truth about Purgatory is almost self-evident to Catholics. However, to many Protestants this is one of the most repugnant of all Catholic teachings. It represents “a medieval invention nowhere to be found in the Bible.” It’s often called “a denial of the sufficiency of Christ’s sacrifice.” It is said to represent “a second-chance theology that is abominable.”
Rejecting the inspiration and canonicity of the Book of Maccabees does not negate its historical value. Maccabees aids us in knowing, purely from an historical perspective at the very least, the Jews believed in praying and making atonement for the dead shortly before the advent of Christ. This is the faith in which Jesus and the apostles were raised. And it is in this context Jesus declares in the New Testament:
"And whoever says a word against the Son of man will be forgiven; but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come "(Matthew 12:32, emphasis added).
This declaration of our Lord implies there are at least some sins that can be forgiven in the next life to a people who already believed it. If Jesus wanted to condemn this teaching commonly taught in Israel, he was not doing a very good job of it according to St. Matthew’s Gospel.’ - Tim Staples
catholic.com/blog/tim-staples/is-purgatory-in-the-bible