The Buddha shares the benefits for a person acting with a pure mind based on his direct knowledge.
Pasannacitta sutta - Pure Mind
This was said by the Blessed One, said by the Arahant, as I have heard:
"Here, bhikkhus, I discern with the mind, after examining a certain person with a pure mind as follows: 'If this person were to die at this very moment, they would be reborn in heaven, just as if they were carried and placed there.' What is the reason for this? Because, bhikkhus, their mind is pure. Indeed, due to the clarity of mind, bhikkhus, some beings, after the breakup of the body, after death, are reborn in a good destination, in a heavenly world."
The Blessed One spoke on this matter. In this regard, it is said:
"Having known a certain person here, to have a pure mind; The Buddha explained this matter, in the presence of the bhikkhus —
If this person were to die, at this very moment; They would be reborn in heaven, for their mind is pure.
Just as one might carry something and set it down, so too is such a person [placed in heaven]; Indeed, due to the clarity of mind, beings go to a good destination."
This matter too was spoken by the Blessed One, as I have heard.