4.
The Discourse on Suddhika
836.
"Monks, there are these four bases for spiritual power.
Which four?
Here, monks, a monk develops the basis for spiritual power that possesses concentration due to desire and volitional activities of striving, concentration due to energy, etc.
concentration due to mind, etc.
he develops the basis for spiritual power that possesses concentration due to investigation and volitional activities of striving -
these, monks, are the four bases for spiritual power."
The fourth.