四分律行事鈔資持記 2.741

2.741

十二。（佛在毘舍離，梨車子多行邪行，披黑毛氈夜行，使人不見，六群學作招譏而制。）

Twelve. (The Buddha was in Vaiśālī. Licchavi youths engaged in much deviant conduct, wearing black wool felt to walk at night so people could not see them. The group-of-six emulated this and invited criticism, so it was prohibited.)