Its source is "Shibunritsu Gyojisho" (one of commentaries of Vinaya Pitaka (ancient sutras in India)) written by Dosen (in pinyin, Daoxuan), a priest who lived in the era of the Tang Dynasty and was honorifically called Nanzan Daishi (Great Priest Nanshan).
典拠は唐の南山大師道宣が著した『四分律行事鈔』。