俱舍論記 15.141

15.141

「是善而劣」者，答。下地捨受，劣善所感。問：上地捨受，勝善能感。何故三定已下捨受，劣善所感？解云：上地更無喜、樂可欣，故勝善能感。下地更有喜、樂二受，人多欣彼不多求捨，為求喜、樂，故勝善感。若不別欣喜、樂二受，但願脫苦，即用劣善感彼捨受。又《婆沙》一百一十五云「問：何故捨根唯善業感，非不善耶？答：捨根行相微細寂靜，智者所樂，故善業感。諸不善業性是麁動，故不能感捨受異熟。

Regarding "It is wholesome, yet inferior," this is an answer: equanimity feeling in the lower stages is brought about by inferior wholesome [karma]. Question: Equanimity feeling in the higher stages can be brought about by superior wholesome [karma]; why is equanimity feeling from the third dhyāna downwards brought about by inferior wholesome [karma]? Explanation: In the higher stages, there is no joy or pleasure to be desired, and thus superior wholesome [karma] can bring it about. In the lower stages, there still exist the two feelings of joy and pleasure; people mostly desire them and do not much seek equanimity. To seek joy and pleasure, superior wholesome [karma] brings them about. If one does not specifically desire the two feelings of joy and pleasure, but merely wishes to be free from pain, one uses inferior wholesome [karma] to bring about that equanimity feeling. Furthermore, the Mahāvibhāṣā, fascicle 115, says: "Question: Why is the faculty of equanimity brought about only by wholesome karma and not by unwholesome karma? Answer: The aspect of the faculty of equanimity is subtle and peaceful, delighting the wise; therefore wholesome karma brings it about. All unwholesome karma is by nature coarse and agitated, so it cannot bring about the ripening of equanimity feeling."