阿彌陀經要解 1.72

1.72

心性寂而常照故為光明，今徹證心性無量之體，故光明無量也。十方三世諸佛皆悉徹證心性全體，皆悉照十方國無所障礙，皆可名無量光，而由因中願力不同，各隨因緣以立別名。今佛昔為法藏比丘，所發四十八願曾有光明恒照十方之願，故今果成如先所願也。法身光明竪窮橫遍故無量，報身光明稱真法性故無量，此則佛佛道同。若夫應身光明，則有或照一由旬者，或照十旬百旬千旬者，或照一世界者，或照十百千世界者，惟彌陀普照十方無量世界，故別名無量光。然三身不一不異，為令眾生得四益故強作此分別耳。

The nature of the mind is quiescent yet constantly illumining, which is why it is light; now, having thoroughly realized the measureless essence of the nature of the mind, his light is therefore measureless. The Buddhas of the ten directions and the three times have all thoroughly realized the entire essence of the nature of the mind, and all illuminate the lands of the ten directions without obstruction; all may be called 'Measureless Light'. Yet because the vow-powers in their causal stages were different, specific names are established for each in accordance with their causes and conditions. In the past, when the present Buddha was the bhikṣu Dharmākara, among the forty-eight vows he made there was a vow that his light would constantly illuminate the ten directions; therefore, now that the fruit is accomplished, it is just as he formerly vowed. The light of the dharmakāya vertically exhausts [all time] and horizontally pervades [all space], and is therefore measureless; the light of the saṃbhogakāya accords with true dharmatā, and is therefore measureless: in this, all Buddhas share the same path. As for the light of the nirmāṇakāya, there are some that illuminate one yojana, or ten, a hundred, or a thousand yojanas; or some that illuminate one world realm, or ten, a hundred, or a thousand world realms; only Amitābha universally illuminates the measureless world realms of the ten directions, and is therefore specifically named 'Measureless Light'. However, the three bodies are neither one nor different; it is only to enable sentient beings to obtain the four benefits that this distinction is forcefully made.