大方廣圓覺修多羅了義經略疏 1.814

1.814

五力者，即前五根增長，魔梵等不能屈伏。又能損滅不信等障，故名為力。

The five powers: namely, the preceding five faculties having grown, Māra, Brahmā, and others cannot subdue them. Furthermore, they can diminish and eliminate obstacles such as lack of faith; therefore they are called powers.