俱舍論記 23.10

23.10

「自性念住至三種念住」者，此釋初章。自性念住以聞、思、修三慧為體，即此三慧亦名三種念住。言釋名者，自性是慧，名念住者，慧由念住，或令念住，故名自性念住。

Regarding "The foundation of mindfulness as intrinsic nature ... the three kinds of foundations of mindfulness": this explains the first heading. The foundation of mindfulness as intrinsic nature takes the three prajñās of listening, reflecting, and cultivating as its essence; these three prajñās are also termed the three kinds of foundations of mindfulness. As for explaining the name: the intrinsic nature is prajñā; the reason it is called a foundation of mindfulness is that prajñā abides by means of mindfulness, or it causes mindfulness to abide, and therefore it is called the foundation of mindfulness as intrinsic nature.