四分律刪繁補闕行事鈔 1.52

1.52

第四用諸部文意。統明律藏，本實一文，但為機悟不同，致令諸計岳立。所以隨其樂欲，成立己宗，競采大眾之文，用集一家之典。故有輕重異勢，持犯分塗；有無遞出，廢興互顯。

Fourth: The intent in utilizing texts of the various schools. Clarifying the Vinaya Piṭaka comprehensively, it was originally truly one text; yet because capacity and awakening differed, various doctrines arose like mountains. Therefore, following their inclinations, they established their own schools, vying to extract texts of the Mahāsāṃgha to compile the canons of their single houses. Hence there came to be differing weights of lightness and heaviness, and divided paths of observance and transgression; existence and nonexistence appeared alternately, and abrogation and establishment became manifest by turns.