大方廣圓覺修多羅了義經略疏 1.813

1.813

五根者，信、進、念、定、慧，此五通生出世間法。由前三科此不可拔，故前三至此總得名根。

The five faculties: faith, diligence, mindfulness, samādhi, and prajñā. These five universally give rise to supramundane dharmas. Because through the preceding three categories these cannot be uprooted, from the preceding three down to this point they collectively obtain the name 'faculties.'