Purgatory
Matthew 12:32
And whosoever shall speak a word against the Son of man, it shall be forgiven him: but he that shall speak against the Holy Ghost, it shall not be forgiven him, neither in this world, nor in the world to come.
Context of the passage
Jesus warns the Pharisees, who had just attributed his exorcisms to the devil, about the unforgivable nature of blasphemy against the Holy Spirit.
Catholic reading
By stating that certain sins are not forgiven 'in this world, nor in the world to come,' Jesus implies by contrast that other sins can indeed be forgiven in the world to come, a state of purification after death distinct from both heaven and hell, i.e., Purgatory.
Common objection
This is simply an emphatic Semitic idiom meaning 'never, ever,' with no intended implication about forgiveness of other sins after death.
Response
Even as an idiom, the phrase's rhetorical force depends on the concept of the 'world to come' being a real time when forgiveness could conceivably occur, an assumption early Fathers and Jewish tradition alike connected with purification after death rather than dismissing outright.