妙法蓮華經玄義 8.128

8.128

別教菩薩，稟此四門之教，因見佛性住大涅槃，故此四句即是別教之四門。一往用擬別門經文，或時為圓門，此義在下料簡（云云）。

Bodhisattvas of the distinctive teaching receive the instruction of these four gates, and through seeing the Buddha-nature they abide in the Great Nirvāṇa; hence these four propositions are the four gates of the distinctive teaching. As an initial classification, they are applied to the sūtra passages of the distinctive gate, or at times they serve as the perfect gate; this meaning will be evaluated below (and so forth).