The Related Suttas Collection 51.23

3. The Iron Ball

A Bhikkhu

“Bhikkhus, there are these four bases of psychic power. What four? It’s when a bhikkhu develops the basis of psychic power that has samādhi due to enthusiasm … energy … mental development … inquiry, and active effort. These are the four bases of psychic power. By developing and cultivating these four bases of psychic power, a bhikkhu realizes the undefiled freedom of heart and freedom by wisdom in this very life. And they live having realized it with their own insight due to the ending of defilements.”