From its first pages, Sacred Scripture speaks to us of the Jewish custom of praying for the dead. This custom necessarily expresses the existence of a place for departed souls which is neither in hell nor in heaven because neither the damned nor the blessed have any need of our prayers.
Still more expressively does the Bible speak to us of the sacrifices for the departed souls which the Jews offered in the Temple. Upon the death of Aaron, they came to offer sacrifices for thirty consecutive days (Dt 34:8; Num 20:30), Judas Machabeus, after the bloody battles, collected sums of money to be sent to Jerusalem in order to have sacrifices offered for the souls of those soldiers who died in battle: “It is therefore a holy and wholesome thought to pray for the dead that may be loosed from their sins” (2 Mac 12:46). Even the prophet Malachi speaks to us of the Lord who purifies with fire the souls of the sons of Levi (cf. Mal 3:3).
Jesus in the New Testament referred to Purgatory more than once. The clearest reference is that of the necessity of settling all our accounts with our enemy before falling into the hands of the Judge who will throw us into prison and from which we will not be released until we have paid “the last penny” (Mt 5:25-26). It is clear that this “prison” cannot be hell, from which one does not come out “forever”, but is Purgatory, as the Holy Fathers of the Church have interpreted it.
St. Paul continues the teaching of Jesus by saying that he who accomplishes imperfect works will save himself, yes, but by passing “through fire” (1 Cor 3:15).
In the same way, after St. Paul, we can also quote the Great Fathers and Doctors of the Church: St. Augustine, St. John Chrysostom, St. Ephrem, St. Cyprian, St. Thomas Aquinas and others. Finally, the Magisterium of the Church, has presented the reality of Purgatory as a dogma of faith.