法界次第初門 1.121

1.121

三、壽者。於名、色、陰、入、界等法中，妄計有我受一期果報，壽有長短，故名壽者。

Third is the living being (jīva / āyuṣmat). Regarding dharmas such as nāmarūpa, the skandhas, āyatanas, and dhātus, one falsely imputes that there is a self undergoing a single span of retribution, with a lifespan that is long or short; therefore it is named living being.