法苑珠林 3.31

3.31

依智度論云。諸天業報生身光者。欲界諸天身常光明。以燈燭明珠等施及持戒禪定等清淨故。身常光明不須日月所照。色界諸天行禪離欲。修習火三昧故。身常出妙光明勝於日月及欲界果報光明離欲天。取要言之。是諸光明皆由心清淨故。得若論釋。佛常光面各一丈。諸天光明大者雖無量由旬。於丈光邊蔽而不現。

According to the Mahāprajñāpāramitā-śāstra: Regarding the bodily radiance born of the karmic retribution of the devas, the bodies of the devas of the Kāmadhātu are constantly radiant. Because they gave lamps, candles, bright pearls, and so forth, and upheld pure morality and meditative absorption, their bodies are constantly luminous without needing the illumination of the sun and moon. The devas of the Rūpadhātu practice dhyāna, transcend desire, and cultivate the fire-samādhi; therefore their bodies constantly emit wonderful radiance surpassing that of the sun and moon and the karmic retribution radiance of the Kāmadhātu. In the desireless heavens, to state the essentials, all these radiances are obtained because of purity of mind. According to the commentary's explanation, the Buddha's regular radiance extends one zhang on each side. Although the radiance of the great devas may extend for immeasurable yojanas, beside this one-zhang radiance it is eclipsed and does not appear.