金光明最勝王經疏 3.17

3.17

贊曰：明無常也。非諸法本如自性身。具足大用不顯現者，所成功德非頓現起，隨利生緣方始起故。如薩婆多云「世尊有受用法。逮初成佛時一時起得，用不頓起。」此亦如是。或約現涅槃云用不顯現，是應身用故。

Commentary: Explaining impermanence. It is not the root of all phenomena like the svābhāvikakāya. That 'its complete great functions are not manifest' means that the virtues accomplished do not arise all at once, but only arise as conditions for benefiting sentient beings occur. As the Sarvāstivādins say: 'The World-Honoured One possesses the dharma of enjoyment. When he first attained Buddhahood, he attained them all at once, but their functions do not arise all at once.' This is also like that. Alternatively, regarding the manifestation of nirvāṇa, it is said that the function is not manifest, because this is the function of the saṃbhogakāya.