四分律比丘含注戒本 1.462

1.462

The Buddha was in Vaiśālī. The Licchavi youths engaged in many perverse deeds, making blankets of black wool and wrapping their bodies in them to walk about at night so that people could not see them. The group of six bhikṣus saw this and deliberately made them as well, which the Licchavis criticized. Bhikṣus raised the fault, and the Buddha laid down the precept on that basis.