法華論疏 2.468

2.468

所以令證法身不退轉者，示現欲與其無量智業故，即是用也。取不退轉者示現欲與其，即用也，亦得無量智業故。釋經中入佛知見道，道即是業也。

The reason for causing them to realize the dharmakāya and not retrogress is because of manifesting the desire to bestow upon them the activity of immeasurable wisdom, which is precisely the function. Taking "not retrogressing" means manifesting the desire to bestow upon them—that is, the function—also because they attain the activity of immeasurable wisdom. It explains "entering the path of the Buddha's knowledge and vision" in the sūtra; "path" is precisely "activity."