俱舍論疏 22.59

22.59

論「有餘於此至說樂亦名苦」，鳩摩邏多釋也。樂受體非是苦，以三因故名為苦，一能為苦因故、二能集眾苦故、三有苦希樂故。由此三因說樂為苦。

On the Śāstra's statement, "Others in this regard... speak of pleasure also as suffering": This is Kumāralāta's explanation. The essence of pleasant sensation is not suffering; it is called suffering due to three causes: first, because it can serve as a cause of suffering; second, because it can accumulate all sufferings; third, because having suffering, one hopes for pleasure. Due to these three causes, pleasure is spoken of as suffering.