俱舍論疏 12.38

12.38

論「此後復有至壽方漸減」，大文第三明住劫。就中有五：一明成次第、二明初唯減、三明中下上、四明後唯增、五總結前。此即初也。從成有情世間十九中劫，人壽無量歲，漸下一有情至阿毘地獄，名成劫已。自此已後，人命漸減。

On the Śāstra's text, "After this there are further... only then does life span gradually decrease": This is the third major section, explaining the kalpa of abiding. Within it there are five parts: first, explaining the order of formation; second, explaining that the beginning is solely decreasing; third, explaining the middle decrease and increase; fourth, explaining that the end is solely increasing; fifth, a general summary of the preceding. This is the first. From the formation of the world of sentient beings across nineteen intermediate kalpas, when human lifespan was immeasurable years, gradually down to a single sentient being [born in] the Avīci hell, it is named the completion of the kalpa of formation. From this point onward, human lifespan gradually decreases.