妙法蓮華經玄贊 2.294

2.294

贊曰：上來合是受用大因，佛在宣揚。自下四因滅後行化，即分為四，此即攝取諸佛轉法輪因，論云「法輪不斷故」。

The commentary states: All of the above constitutes the great cause of experiential fruition, when the Buddha was present and expounding it. From here on, the four causes pertain to carrying out teaching after his extinction, divided into four. This is the cause of upholding the buddhas' turning of the wheel of the Dharma, as the treatise says: "Because the wheel of the Dharma is uninterrupted."