俱舍論疏 7.135

7.135

論「有餘師說至通起三種」，述異說也。此師意說入聖難，唯共相作意；出心易故，通三作意。

The Śāstra says, "Other masters say ... universally gives rise to the three": this recounts an alternative explanation. What this master means is that entering the noble is difficult, so it is solely attention to general characteristics; since the mind that emerges is easy, it extends to all three types of attention.