[506] And how does a bhikkhu develop the basis of success (iddhipāda) that possesses concentration due to zeal and volitional formations of striving (chandasamādhi-padhānasaṅkhāra)?
If a bhikkhu, having made zeal (chanda) dominant (adhipati), gains concentration (samādhi), gains one-pointedness of mind (citta), this is called concentration due to zeal (chandasamādhi). For the non-arising of unarisen evil, unwholesome phenomena (dhammā) he generates zeal, endeavors, arouses energy, exerts his mind, and strives; for the abandoning of arisen evil, unwholesome phenomena he generates zeal, endeavors, arouses energy, exerts his mind, and strives; for the arising of unarisen wholesome phenomena he generates zeal, endeavors, arouses energy, exerts his mind, and strives; for the persistence, non-loss, increase, abundance, development, and fulfillment of arisen wholesome phenomena he generates zeal, endeavors, arouses energy, exerts his mind, and strives. These are called volitional formations of striving (padhānasaṅkhārā).
Thus this concentration due to zeal and these volitional formations of striving, having been gathered together and condensed into one, come to be reckoned simply as "concentration due to zeal and volitional formations of striving" (chandasamādhi-padhānasaṅkhāra).
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.