四分律比丘含注戒本 1.454

1.454

佛在曠野國。六群比丘至養蠶家，索未成綿及已成綿，并雜野蠶綿，以作臥具，又看暴繭。居士譏嫌，言「害生命，無有正法」。比丘舉過，佛因制戒。

The Buddha was in the country of Aṭavī. The group of six bhikṣus went to silkworm breeders to seek unspun silk and spun silk, as well as mixed wild silk, in order to make rugs, and they also watched the cocoons being boiled in the sun. Householders criticized and reproached them, saying, 'They harm living beings; they have no true Dharma.' The bhikṣus reported the fault, and the Buddha thereupon formulated the precept.