Christianity teaches that after death, humans’ souls go to purgatory to atone for the sins committed during their life on earth. However, the true evolution of humans occurs on earth, not anywhere else.

Those who, because of their crimes, are condemned to suffer a long time in the regions of the astral plane – called purgatory – after their death must subsequently return to earth to make good the wrong they have done.

It is not enough to suffer, because suffering is no reparation for all the mistakes they have made.

Humans make mistakes on earth and they therefore have to return to earth to make amends. There is no other explanation for reincarnation.

If they had already atoned for their errors up above, why should they have to come back to earth? There is in fact a law which dictates that human beings must put right their mistakes in all the regions of the universe where these mistakes caused harm, and therefore also in the physical realm. This is how they grow and learn.
Omraam Mikhaël Aïvanhov