金光明最勝王經疏 2.9

2.9

言釋名者，三身諸佛俱號如來。壽即是命。量謂限量，或謂量度。即量度貶量佛壽之限齊，即如來之壽量，或如來壽之量，皆依主釋。即任法性而凝然，隨願緣而相續，應物機而無斷，壽德難測。即依法性持功德相決定凝湛，是法身命根。如佛及土性相有異，此亦應爾。或即功德相自凝然能持自體，名為壽量。依鏡智種，由大願種力，令四智品決定相續，盡眾生界，是報身壽。由大悲種力，隨生感緣，現色蘊身決定分限，是他受變化二身壽。體許假立，故思亦願收，不違《唯識》由業所引。

Regarding the explanation of the title: The Buddhas of the three bodies are all called tathāgata. 'Span' (壽) is life. 'Measure' (量) means limit, or it means measurement. That is, measuring and assessing the limits of the Buddha's life-span; it is the Tathāgata's life-measure, or the measure of the Tathāgata's life—both are genitive determinative compounds (tatpuruṣa). That is, it abides continuously by resting in the Dharma-nature, it continues in succession in accordance with vows and conditions, and it is uninterrupted in responding to the capacities of beings; the virtue of this life-span is hard to fathom. Resting upon the Dharma-nature to uphold the aspects of virtue, decisively tranquil and clear—this is the life-faculty of the Dharma body. Just as the Buddha and the land differ in nature and characteristics, so too should this be understood. Or, the aspects of virtue themselves, abiding calmly, are able to uphold their own substance, which is called the life-measure. Resting upon the seeds of the mirror-like wisdom, through the power of the seeds of the great vow, it causes the four categories of wisdom to continue in decisive succession to the end of the realm of sentient beings; this is the life-span of the reward body. Through the power of the seeds of great compassion, in accordance with the conditions of beings' responses, it manifests a body of the form aggregate with decisive limits; this is the life-span of the two bodies of other-enjoyment and transformation. Since their substance is conceded to be conventionally established, volition (cetanā) is also included under vow, which does not contradict Vijñaptimātra's doctrine that it is drawn by karma.