法華論疏 2.126

2.126

七者入甚深者，名字章句意難得故，自在住持，不同外道說因緣法，名為甚深，

[The Treatise says:] "Seventh is the profundity of entry, because the meaning of words, sentences, and verses is difficult to attain, and he abides and sustains them with sovereign mastery, unlike non-Buddhists who speak of the dharma of causes and conditions; [hence] it is called profundity,"