妙法蓮華經玄義 6.102

6.102

脩多羅者，諸經中直說者，謂四《阿含》，及二百五十戒，出三藏外諸摩訶衍經直說者，皆名脩多羅也。

As for *sūtra*, the direct prose discourses in the various scriptures—meaning the four *Āgamas* and the two hundred and fifty precepts, as well as the direct prose discourses in the various Mahāyāna scriptures outside the Tripiṭaka—are all named *sūtra*.