法界次第初門 2.168

2.168

此五通名根者，能生也。行者既得四如意足，智、定安隱，即信等五種善法，若似、若真任運而生。譬如陰陽調適，一切種子悉有根生，故名根也。

These five are collectively called 'faculties' because they are capable of engendering. When the practitioner has attained the four bases of psychic power and wisdom and samādhi are settled, then the five wholesome dharmas such as faith arise spontaneously, whether conformable or real. Just as when yin and yang are harmonious and all seeds sprout roots, they are therefore called faculties.