妙法蓮華經玄義 9.51

9.51

別教四門亦如是，為四機說，故有四；同是佛教，故言一。入實觀異，故言四；俱向一實，故言一。所隨於能，故言四；能會於所，故言一。不即生死是涅槃，教狹小；不即煩惱是菩提，故行狹小。教行取理難當，名理論狹小。

The four gates of the distinctive teaching are also like this: expounded for four capacities, therefore there are four; being equally the Buddha's teaching, therefore called one. Because entry into the contemplation of reality differs, they are called four; because they all head toward the one reality, they are called one. The facilitated follows the facilitating, therefore called four; the facilitating unites with the facilitated, therefore called one. Not [realising] immediately that saṃsāra is nirvāṇa means the teaching is narrow and small; not [realising] immediately that defilements are bodhi means the practice is narrow and small. Because teaching and practice find it difficult to match the principle, it is called narrow and small in terms of principle.