俱舍論疏 23.25

23.25

論「此四念住至不增不減」，此釋念住唯有四也。以對四倒立四念住，倒唯四故，念住亦四。《正理》復云「對治四食」。

[On] the treatise's: "These four applications of mindfulness... neither increase nor decrease", this explains why there are only four applications of mindfulness. Because the four applications of mindfulness are established as counteragents to the four inversions, and since the inversions are only four, the applications of mindfulness are also only four. The Nyāyānusāra also says: "To counter the four nutriments."