律戒本疏 1.28

1.28

第七非親理居士居士婦自恣與衣乃至上下衣應受　前以結戒非親理向乞。好施之人哉。有怨恨。若唯親是福。非親何熟。又諸比丘因緣失衣。無有親理。求之無所。於是世尊復為開。三衣有上中下。有三衣為上。餘為下。若比丘失衣。施者恣與聽。取所少不得過受六肘十八肘。是三衣段為割截故各長一肘也。

Seventh: An unrelated male or female householder freely offering robes, up to the upper and lower robes, which should be accepted. Previously, because of the formulation of the precept that one must not beg from the unrelated, people fond of giving had resentment: "If only relatives [bring] merit, what will ripen for the non-relatives?" Furthermore, various monks lost their robes through causes and conditions and had no relatives, having nowhere to seek them. Thereupon the World-Honoured One opened [the rule] again for them. The three robes comprise upper, middle, and lower: the three robes are the upper, and the rest are the lower. If a monk has lost robes and a donor freely offers them, he is permitted to take what he lacks, but he must not accept in excess: six cubits to eighteen cubits. These are pieces for the three robes; because of cutting, each is lengthened by one cubit.