俱舍論疏 28.103

28.103

論「第三靜慮至足前為十」，明第三靜慮加四支也。一行捨，即善中捨也。二正念，通中念也。三正慧，通中慧也。四樂受，其受若就七十五法以明，即四地受皆同一也。若五受以明，即喜、樂、捨各別也。今就五受以明，故樂受增一。

On the treatise passage: "In the third dhyāna [...] bringing the previous [total] to ten": this explains that the third dhyāna adds four factors. First, equanimity, which is equanimity among wholesome [dharmas]. Second, right mindfulness, which is mindfulness among universal [dharmas]. Third, right discernment, which is discernment among universal [dharmas]. Fourth, pleasurable feeling. If feeling is explained in terms of the seventy-five dharmas, then feeling across all four levels is identical. If explained in terms of the five feelings, joy, pleasure, and equanimity are distinct. Here it is explained in terms of the five feelings; therefore, pleasurable feeling is added as one [more entity].