[1151] Bhikkhus, if a bhikkhu, in dependence on energy (vīriya), obtains concentration (samādhi), obtains one-pointedness of mind (citta) — this is called concentration due to energy. For the non-arising of unarisen … he generates desire (chanda), makes an effort, arouses energy, exerts his mind, and strives for the maintenance, non-confusion, increase, expansion, development, and fulfillment of arisen wholesome states. These are called volitional formations of striving (padhānasaṅkhārā). Thus, this energy, this concentration due to energy, and these volitional formations of striving — this, bhikkhus, is called the basis of spiritual power (iddhipāda) endowed with concentration due to energy and volitional formations of striving.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.