律戒本疏 1.38

1.38

十七非親里尼浣染擗羊毛　迦留陀夷眾中分得羊毛。令尼浣染。既廢道業。又年色變壞。後諸比丘尼眾共往佛所。佛問。何故。具以實答。因是結戒。犯者捨墮。將以親必無惡緣。風塵譏嫌。亦無由而起。故制非親。而許其親理也。

Seventeenth: An unrelated nun washing, dyeing, or carding sheep's wool. Kālodayin obtained sheep's wool as his share in the Saṃgha and ordered a nun to wash and dye it. Not only did she neglect her spiritual practice, but her youthful appearance also deteriorated. Later, the assembly of bhikṣuṇīs went together to the Buddha's place. The Buddha asked what the reason was, and they answered fully with the truth. On this account, the precept was formulated; violators commit a niḥsargika-pāyattika. Because with relatives there are certainly no evil conditions, gossip and disparagement also have no way to arise; therefore it was prohibited for the unrelated, while permitting relatives.