俱舍論疏 13.3

13.3

以三義故名之為業：一者作用、二持法式、三分別果。一作用者，謂即作用說名為業。持法式者，謂能任持七眾法式。分別果者，謂能分別愛、非愛果。此品廣明，故名分別。所以次世品後者，世品明內、外果差別不同。果所賴因謂由業惑，惑總、業別，故先明業。

It is named "karma" due to three meanings: first, activity; second, maintaining the models of Dharma; third, differentiating fruits. First, "activity" means that activity itself is called karma. "Maintaining the models of Dharma" means being able to maintain the Dharma models of the seven assemblies. "Differentiating fruits" means being able to differentiate desirable and undesirable fruits. Because this chapter clarifies it extensively, it is named "Exposition." As for why it follows the Chapter on the World: the Chapter on the World clarifies the differences between internal and external fruits. The causes upon which fruits depend are karma and defilement; defilement is general and karma is specific, hence karma is clarified first.