I Corinthians 3 is the scriptural justification, such as it is, for Purgatory.
10 According to the grace of God given to me, like a skilled master builder I laid a foundation, and someone else is building on it. Each builder must choose with care how to build on it. 11 For no one can lay any foundation other than the one that has been laid; that foundation is Jesus Christ. 12 Now if anyone builds on the foundation with gold, silver, precious stones, wood, hay, straw— 13 the work of each builder will become visible, for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each has done. 14 If what has been built on the foundation survives, the builder will receive a reward. 15 If the work is burned, the builder will suffer loss; the builder will be saved, but only as through fire.
The idea makes some psychological sense. Someone with her heart in the right place might not deserve Hell, but might not yet be fit to enter the presence of God: so be sent to freeze and quake in frigid purgatorial fires, which cleanse her.
However, it reinforced Christianity as a tool of social control. Obey, or however harsh life is here, you will suffer more after you die. In The Karamazov Brothers, Lena, rebelling against the stultifying conventionality which has labelled itself the Christian way has no words for any alternative but evil and wickedness; so in her desperation she cries out to be evil. Living in Christian love should be freedom, but her Orthodoxy is slavery.
The doctrine of purgatory made the Church corrupt. Noble men, who used force and feudal law to compel peasants to work to feed them, who spent their time in armour on horseback murdering other peasants, accumulated wealth to endow chantry chapels, where monks would say masses so that their souls would spend less time in Purgatory. American conservative Evangelicalism is not the first time Christianity has made God weep.
And. There are moments in life when human beings are tested, individual and national Days of Judgment, which Jesus called being “born again” and Paul here calls passing through the fire: metaphors of pain balanced by the rewards offered, “seeing the Kingdom of God”, or being the temple where God dwells.
Why should I care what happens after my death, when I am alive? Humans create ideas of reward and punishment imposed by God, while Jesus and Paul teach of the ordinary consequences of our actions, enforced by objective reality.