四分律比丘含注戒本 1.102

1.102

The Buddha was in Vaiśālī. At that time, grain was expensive in the world and almsfood was difficult to obtain. Those observing the retreat along the Vaggumudā River then mutually praised one another as having attained superhuman dharmas, so faithful lay devotees reduced their own portions to give to them as offerings. Later, when they went to the Buddha's place, [the Buddha] questioned and rebuked them because of this, and formulated this precept.