大方廣圓覺修多羅了義經略疏 1.812

1.812

四神足者，欲、勤、心、觀。欲謂樂欲；勤謂無間；心謂定也，專一境性；觀謂慧也，內自揀擇。以勤過散亂，智火微弱，故須定制，即所欲自在。神即神通，足即是定。由出世法最勝自在，欲等四定能證此故，名為神足，亦名如意足，所欲如心故。

The four bases of psychic power: aspiration, diligence, mind, and contemplation. Aspiration means joyful wishing; diligence means non-interruption; mind means samādhi, single-pointedness on an object; contemplation means prajñā, discerning internally within oneself. Because excessive diligence leads to distraction and makes the fire of wisdom weak, it must be regulated by samādhi, which yields mastery over what is desired. 'Psychic' is psychic powers; 'bases' are samādhi. Because supramundane dharmas are supreme mastery, and the four samādhis such as aspiration can realize this, they are called bases of psychic power; they are also called bases of fulfillment of wishes, because what is desired accords with one's mind.