The mirror discourse was preached in Natika Village.
At that time, Ananda (the attendant monk of Buddha) was reporting to Buddha about disciples who had passed away. He also asked Buddha about their next rebirth. Where did they reborn, what were their fate etc.
Buddha answered with compassion and explained their spiritual attainments and where they were reborn.
It was pretty lengthy as Ananda had a long list!
After that, Buddha explained that anyone endowed with wisdom would be able to know their future state of existence.
Moreover, if the Buddha was to tell the future birth of every disciple who had died, that would not be much benefit.
The Buddha then advised the following.
An ariya disciple who possesses the Mirror of wisdom can voluntarily aspire thus, ” I shall never be reborn in hell, as a preta or as an animal nor any miserable states. I shall only be reborn in fortunate states that leads towards enlightenment.”
The Buddha further explained that to achieve the above aspiration, an Ariya must have unshakeable faith in Buddha, Dharma and Sangha. He or she must also possess moral precepts which tend to break the bondage of Craving.
The above are to be known as the four factors of the Mirror of Wisdom.
In this manner, an Ariya disciple who possess the Mirror of wisdom can be confident of their future rebirth. Need not fear.
May all be well and happy.