俱舍論疏 24.31

24.31

論「即此上流至為極處故」，開為二也。由因、果別分二上流，謂樂定、慧有差別故。由因別者，樂慧上流有雜修定，樂定上流無雜修定。由果別者，樂慧上流生色究竟，不生無色；樂定上流生有頂天，不生淨居。既言二天為極處故，亦容生下淨居、無色。若不爾者，下四淨居、下三無色應無羅漢是半超也。

On the treatise passage, "This very upstream practitioner... because these are the ultimate limits": This divides them into two. Due to differences in causes and results, the upstream practitioner is divided into two, meaning there is a distinction between delighting in samādhi and delighting in wisdom. By difference of cause: the upstream practitioner who delights in wisdom possesses miscellaneous cultivation of dhyāna, whereas the upstream practitioner who delights in samādhi does not possess miscellaneous cultivation of dhyāna. By difference of result: the upstream practitioner who delights in wisdom is reborn in Akaniṣṭha and is not reborn in the formless realm; the upstream practitioner who delights in samādhi is reborn in the heaven of Bhavāgra and is not reborn in the Śuddhāvāsa heavens. Since it states that these two heavens are the ultimate limits, it also allows for rebirth in the lower Śuddhāvāsa heavens and the lower formless heavens. Were it not so, there would be no arhats in the lower four Śuddhāvāsa heavens or the lower three formless heavens; these are intermediate traversers.