佛祖統紀 33.58

33.58

述曰。今人無識多用白布為直掇坐具。違失僧儀最為非法。今請於黑布偏衫之下。著白布衫袴以表制服。二師父母皆同此制。若義家父母亦可例此。隨俗稍用紵布。上不違涅槃諸律之無文。下不棄遠應二師之義開。隨方護法當用中道。

The commentary says: People today lack discernment and mostly use white cloth to make the straight-seam robe and sitting cloth. This violates monastic deportment and is utterly improper. I now propose that beneath a black cloth side-seamed jacket, one should wear white cloth tunic and trousers to signify the mourning dress. This system applies equally to the two masters and to one's parents. If one has adoptive parents, it may also be analogized to this. Conforming to custom, one may use ramie cloth a little. Above, it does not violate the lack of textual mandate in the Nirvāṇa [Sūtra] and the various Vinayas; below, it does not abandon the open dispensations of the two masters Yuan and Ying. Protecting the Dharma according to the region must follow the middle path.