釋禪波羅蜜次第法門 5.146

5.146

復次，初禪樂從外而發，外識相應，意識不相應，內樂不滿；二禪之樂雖從內發，然從喜而生，喜根相應，樂根不相應，樂依於喜，喜尚不遍，況於樂邪？今三禪之樂從內發，以樂為主，內無喜動，念慧因緣，令樂增長遍身，內外充滿，恬愉快樂，世間第一樂中之上，故佛說行慈果報遍淨地中。

Furthermore, the bliss of the first dhyāna arises from the outside and is associated with external consciousness, not with mental consciousness, so internal bliss is not full. Although the bliss of the second dhyāna arises from within, it is generated from joy (prīti); it is associated with the joy-faculty, not with the bliss-faculty. Bliss relies upon joy, and joy does not even permeate [the body], how much less bliss? Now, the bliss of the third dhyāna arises from within and takes bliss as primary; within, there is no agitation of joy, and through the conditions of mindfulness and wisdom, it causes bliss to increase and permeate the body, filling both inside and outside with peaceful joy and happiness—the highest of mundane pleasures. Therefore the Buddha taught that the retribution for practicing loving-kindness is in the stage of Complete Purity (Śubhakṛtsna).